TITLE: A SYSTEM AND METHOD FOR PROVIDING BONUS CREDIT TO A PLAYER FIELD OF THE INVENTION The present invention relates to gaming machines and in particular to systems and methods for providing promotional credit to a player playing a gaming machine and will be described with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use and promotional credit and other non-cash prizes can be used in any other suitable industry such as purchasing goods and other services in any suitable environment. BACKGROUND OF THE INVENTION In this specification unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned. Many gaming venues implement rewards and loyalty programs for customers to reward them for visiting or continuing to visit the venue and for partaking in gaming and other purchases at the venue. These rewards take the form of bonus points, meal vouchers and rewards vouchers that can be used internally within the venue which may be a club, hotel or casino. The rewards of the prior art may be limiting in some cases and it is an object of the present invention in its preferred embodiment to overcome, or at least substantially ameliorate, one or more of the disadvantages of the prior art or at least to provide a useful alternative. SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a system for providing bonus credit to a player, the system including: a gaming machine for providing a game of chance to the player, the player wagering on the outcome of the game by inserting credit into the gaming machine; a central server in communication with the gaming machine for receiving information related to the inserted credit, the central server storing bonus trigger information for comparison with the information related to the inserted credit, the central server sending bonus information to the gaming machine to provide bonus credit to the player based on the comparison of the bonus trigger information and the information related to the inserted credit. 1 Preferably the credit inserted into the gaming machine is in the form of a ticket, the central server storing information related to credit stored on the ticket. In some embodiments the credit is inserted into the gaming machine in the form of cash; a members card; or the like. Preferably the ticket includes player information. Preferably the player information is stored on the central server. In some embodiments, the player information is stored on a player card that is inserted into the gaming machine prior to the ticket. Preferably the ticket includes a plurality of credit types, a first credit type being associated with gaming and being available to wager on the gaming machine, a second credit type being associated with non gaming purchases and not being available to wager on the gaming machine. Preferably the bonus credit provided to the player is the first credit type and can be wagered on the gaming machine. In some embodiments, the bonus credit provided to the player is the second credit type. In further embodiments, the bonus credit provided to the player is a combination of the first credit type and the second credit type. Preferably the bonus credit provided to the player is a multiple of the credit stored on the ticket. Preferably the bonus credit provided to the player is a predetermined multiple of the credit stored on the ticket. In some embodiments the bonus credit provided to the player is a random multiple of the credit stored on the ticket. Preferably the amount of bonus credit provided to the player is based on any one or more of the following: time of day; day of the week; player information; accumulated player reward points; player loyalty; player status or any other suitable criteria. Preferably the ticket is a reusable ticket onto which new credit information is stored when the player cashes out. In other embodiment the ticket is a single use ticket and the gaming machine prints a new ticket when the player cashes out. Preferably the player can redeem credit stored on the ticket for cash at a cashier. Preferably, the player can redeem the first credit type and/or the second credit type for cash at a cashier. In some embodiments only the first credit type can be redeemed for cash and the second credit type can only be used to purchase non gaming related goods and/or services. That is, the second credit type must be spent at the venue and cannot be redeemed for cash. According to a second aspect of the invention there is provided a method for providing bonus credit to a player, the method including the steps of: providing a gaming machine for providing a game of chance to the player, the player wagering on the outcome of the game by inserting credit into the gaming machine; 2 providing a central server in communication with the gaming machine for receiving information related to the inserted credit, the central server storing bonus trigger information for comparison with the information related to the inserted credit, the central server sending bonus information to the gaming machine to provide bonus credit to the player based on the comparison of the bonus trigger information and the information related to the inserted credit. Preferably the method includes the step of inserting credit into the gaming machine in the form of a ticket and the step of the central server storing information related to credit stored on the ticket. In some embodiments the credit is inserted into the gaming machine in the form of cash; a members card; or the like. Preferably the ticket includes player information. Preferably the method includes the step of the player information being stored on the central server. In some embodiments, the player information is stored on a player card that is inserted into the gaming machine prior to the ticket. Preferably the method includes the step of providing the ticket with a plurality of credit types, a first credit type being associated with gaming and being available to wager on the gaming machine, a second credit type being associated with non gaming purchases and not being available to wager on the gaming machine. Preferably the bonus credit provided to the player is the first credit type and can be wagered on the gaming machine. In some embodiments, the bonus credit provided to the player is the second credit type. In further embodiments, the bonus credit provided to the player is a combination of the first credit type and the second credit type. Preferably the bonus credit provided to the player is a multiple of the credit stored on the ticket. Preferably the bonus credit provided to the player is a predetermined multiple of the credit stored on the ticket. In some embodiments the bonus credit provided to the player is a random multiple of the credit stored on the ticket. Preferably the amount of bonus credit provided to the player is based on any one or more of the following: time of day; day of the week; player information; accumulated player reward points; player loyalty; player status or any other suitable criteria. Preferably the ticket is a reusable ticket onto which new credit information is stored when the player cashes out. In other embodiment the ticket is a single use ticket and the gaming machine prints a new ticket when the player cashes out. Preferably the method includes the step of the player redeeming credit stored on the ticket for cash at a cashier. Preferably, the method includes the step of the player redeeming the first credit type and/or the second credit type for cash at a cashier. In some embodiments only the first credit type can be redeemed for cash and the second credit type can only be used to purchase non gaming related goods and/or services. That is, the second credit type must be spent at the venue and cannot be redeemed for cash. 3 Throughout the specification and claims which follow, unless the context requires otherwise, the word "comprise", and other variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers of steps. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 a is a diagram of a gaming machine according to the invention; Figure lb is a diagram of another gaming machine according to the invention; Figure 2 is a diagram of another gaming machine according to the invention; and Figure 3 is a flowchart according to the invention. PREFERRED EMBODIMENT OF THE INVENTION The preferred embodiment of the invention discloses a system for providing bonus credit to a player. The system includes a gaming machine for providing a game of chance to the player, the player wagering on the outcome of the game by inserting credit into the gaming machine. A central server is in communication with the gaming machine for receiving information related to the inserted credit. The central server also stores bonus trigger information for comparison with the information related to the inserted credit to determine whether bonus credit is to be awarded and provided to the player. The central server sends bonus information to the gaming machine to provide bonus credit to the player based on the comparison of the bonus trigger information and the information related to the inserted credit. In the preferred embodiment the credit inserted into the gaming machine is in the form of a ticket, the central server storing information related to credit stored on the ticket. One such ticket system is described in applicant's Australian patent application numbers 2009900874 and 2009900872 filed 27 February 2009, the contents of which are incorporated herein by way of reference. In other embodiments the gaming machine accepts credit in the form of cash, credit cards, EFTPOS cards, members cards, tokens and the like and any suitable payment means can be accepted. In the preferred embodiment the ticket is reusable and includes player information which is stored on the central server. In other embodiments, the player information is stored on a player card that is inserted into the gaming machine prior to the ticket or other type of credit. In either embodiment, additional player information is preferably stored on the central server. The player information includes any predetermined information that may 4 be required or monitored by the gaming venue and may include historical player gaming information such as the frequency they game at the venue, the average player wager size, the net winnings or loss of the player that visit and historically, player gaming revenue and any other information that may be collected by the venue. The ticket preferably includes a plurality of credit types, a first credit type being associated with gaming and being available to wager on the gaming machine, a second credit type being associated with non gaming purchases and not being available to wager on the gaming machine. It would be understood that in some embodiments it may be advantageous to include a single type of credit only. In the preferred embodiment the bonus credit awarded can only be used for gaming and cannot be used for purchases of goods and/or services. However, it is preferred that any winnings from the bonus credit be available to the player to purchase as they wish on gaming or on non gaming goods and/or services. As such, it is preferred that the bonus credit provided to the player is the first credit type and can be wagered on the gaming machine. In some alternative embodiments, the bonus credit provided to the player is the second credit type. In further embodiments, the bonus credit provided to the player is a combination of the first credit type and the second credit type. It would be understood that the credit type can be determined by the venue or may be required by legislation in some jurisdictions. The system is flexible and can be configured according to the specific requirements of the venue. The bonus credit provided to the player is a preferably a multiple of the credit stored on the ticket. In some cases the bonus credit is a predetermined multiple of the credit stored on the ticket and in other embodiments the bonus credit provided to the players is random or a random multiple of the credit stored on the ticket. Typically, it is preferred that the multiple is one of: 1x; 1.5x; 2x; 3x; 4x; 5x; 6x; 7x; 8x; 9x; or lOx however any suitable multiple can be used. The multiple may also vary according to the requirements of the venue and may vary automatically or manually by an operator. The bonus credit need not be a multiple of the credit inserted and can be a predetermined or random amount which is independent of the credit inserted. In some embodiments, the amount of bonus credit provided to the player is based on any one or more of the following: time of day; day of the week; player information; accumulated player reward points; or any other suitable criteria. As would be understood it may be advantageous to provide additional credit to players when the gaming venue is typically quiet, such as 12am to 7am or any other applicable times. The venue may choose to provide a predetermined bonus time period or "happy hour" for example, from 5pm to 6pm, during which all players receive an additional bonus credit of 2x their wager or the like between 5pm and 6pm daily. Any suitable combination thereof can also be implemented according to the requirements of the venue. For example, bonus credit may be provided, say, on all wagers placed Monday Thursday 12am to 7am and happy hour is provided every Saturday and Sunday. The central server can be configured to automatically keep track of the different bonus credit 5 times through a schedule calendar accessible to an administrator of the central server. The administrator is able to amend and update the schedule as required through a administrator interface which is preferably a web interface to the central server. In some embodiments bonus credit is provided only to registered players and is provided based on the historical player wagering information. For example, a player may receive $100 bonus credit for each $1000 wagered or may receive a bonus of $50 whenever the player's wagering turnover reaches $500. A bonus schedule can also be implemented specifically for each registered player based on that player's gaming history. For example, player A, a casual gamer, may receive the standard "happy hour" bonus of 2x their wager, but player B, a more frequent game, may receive 4x their wager during the same "happy hour". In the preferred embodiment the ticket is a reusable ticket onto which new credit information is stored when the player cashes out. In other embodiments the ticket is a single use ticket and the gaming machine prints a new ticket when the player cashes out. In some embodiments, the gaming machine prints out a separate ticket for each credit type. In the preferred embodiment the player can redeem all the credit stored on the ticket for cash at a cashier. In some embodiments the player can only redeem the first credit type or the second credit type for cash at a cashier. In some embodiments only the first credit type can be redeemed for cash and the second credit type can only be used to purchase non gaming related goods and/or services such as food, transport, goods from shops and the like. Gaming machines according to the preferred embodiment of the invention will now be described with reference to the drawings. In one embodiment, as illustrated in Fig. lA, the gaming device includes one or more display devices controlled by the processor. The display devices are preferably connected to or mounted to the cabinet of the gaming device. The embodiment shown in Fig. 1A includes a central display device 16 which displays a primary game. This display device may also display any suitable secondary game associated with the primary game as well as information relating to the primary or secondary game. The alternative embodiment shown in Fig. 1A includes a central display device 16 and an upper display device 18. The upper display device may display the primary game, any suitable secondary game associated or not associated with the primary game and/or information relating to the primary or secondary game. These display devices may also serve as digital glass operable to advertise games or other aspects of the gaming establishment. The gaming device includes a credit display which displays a player's current number of credits, cash, account balance or the equivalent. In one embodiment, the gaming device includes a bet display which displays a player's amount wagered. In one embodiment, as described in more detail below, the gaming device includes a player tracking display which displays information regarding a player's playing tracking status. 6 In another embodiment, at least one display device may be a mobile display device, such as a PDA or tablet PC, that enables play of at least a portion of the primary or secondary game at a location remote from the gaming device. The display devices may include, without limitation, a monitor, a television display, a plasma display, a liquid crystal display (LCD) a display based on light emitting diodes (LED), a display based on a plurality of organic light-emitting diodes (OLEDs), a display based on polymer light-emitting diodes (PLEDs), a display based on a plurality of surface-conduction electron-emitters (SEDs), a display including a projected and/or reflected image or any other suitable electronic device or display mechanism. In one embodiment, as described in more detail below, the display device includes a touch screen with an associated touch-screen controller. The display devices may be of any suitable size and configuration, such as a square, a rectangle or an elongated rectangle. The display devices of the gaming device are configured to display at least one and preferably a plurality of game or other suitable images, symbols and indicia such as any visual representation or exhibition of the movement of objects such as mechanical, virtual or video reels and wheels, dynamic lighting, video images, images of people, characters, places, things and faces of cards, and the like. In one alternative embodiment, the symbols, images and indicia displayed on or of the display device may be in mechanical form. That is, the display device may include any electromechanical device, such as one or more mechanical objects, such as one or more rotatable wheels, reels or dice, configured to display at least one or a plurality of game or other suitable images, symbols or indicia. As illustrated in Fig. 1A, in one embodiment, the gaming device includes at least one payment device 24 in communication with the processor. A payment device such as a payment acceptor includes a note, ticket or bill acceptor 28 wherein the player inserts paper money, a ticket or voucher and a coin slot 26 where the player inserts money, coins, or tokens. In other embodiments, payment devices such as readers or validators for credit cards, debit cards or credit slips may accept payment. In one embodiment, a player may insert an identification card into a card reader of the gaming device. In one embodiment, the identification card is a smart card having a programmed microchip or a magnetic strip coded with a player's identification, credit totals (or related data) and other relevant information. In another embodiment, a player may carry a portable device, such as a cell phone, a radio frequency identification tag or any other suitable wireless device, which communicates a player's identification, credit totals (or related data) and other relevant information to the gaming device. In one embodiment, money may be transferred to a gaming device through electronic funds transfer. When a player funds the gaming device, the processor determines the amount of funds entered and displays the corresponding amount on the credit or other suitable display as described above. In one embodiment, as mentioned above and seen in Fig. 1A, one input device is a touch screen 42 coupled with a touch-screen controller 44, or some other touch-sensitive 7 display overlay to allow for player interaction with the images on the display. The touch screen and the touch-screen controller are connected to a video controller 46. A player can make decisions and input signals into the gaming device by touching the touch screen at the appropriate places. One such input device is a conventional touch-screen button panel. The gaming device may further include a plurality of communication ports for enabling communication of the processor with external peripherals, such as external video sources, expansion buses, game or other displays, an SCSI port or a key pad. In one embodiment, as seen in Fig. 1A, the gaming device includes a sound generating device controlled by one or more sounds cards 48 which function in conjunction with the processor. In one embodiment, the sound generating device includes at least one and preferably a plurality of speakers 50 or other sound generating hardware and/or software for generating sounds, such as playing music for the primary and/or secondary game or for other modes of the gaming device, such as an attract mode. In one embodiment, the gaming device provides dynamic sounds coupled with attractive multimedia images displayed on one or more of the display devices to provide an audio-visual representation or to otherwise display full-motion video with sound to attract players to the gaming device. During idle periods, the gaming device may display a sequence of audio and/or visual attraction messages to attract potential players to the gaming device. The videos may also be customized for or to provide any appropriate information. In one embodiment, the gaming machine may include a sensor, such as a camera in communication with the processor (and possibly controlled by the processor) that is selectively positioned to acquire an image of a player actively using the gaming device and/or the surrounding area of the gaming device. In one embodiment, the camera may be configured to selectively acquire still or moving (e.g., video) images and may be configured to acquire the images in either an analog, digital or other suitable format. The display devices may be configured to display the image acquired by the camera as well as display the visible manifestation of the game in split screen or picture-in-picture fashion. For example, the camera may acquire an image of the player and the processor may incorporate that image into the primary and/or secondary game as a game image, symbol or indicia. Gaming device 10 can incorporate any suitable wagering primary and/or base game. The gaming machine or device may include some or all of the features of conventional gaming machines or devices. The primary or base game may comprise any suitable reel type game, card game, cascading or falling symbol game, number game or other game of chance susceptible to representation in an electronic or electromechanical form, which in one embodiment produces a random outcome based on probability data at the time of or after placement of a wager. That is, different primary wagering games, such as video poker games, video blackjack games, video keno, video bingo or any other suitable primary or base game may be implemented. 8 In one embodiment, as illustrated in Fig. IB, one or more of the gaming devices 10 are in communication with each other and/or at least one central server, central controller or remote host 56 through a data network or remote communication link 58. In this embodiment, the central server, central controller or remote host is any suitable server or computing device which includes at least one processor and at least one memory or storage device. In different such embodiments, the central server is a progressive controller or a processor of one of the gaming devices in the gaming system. In these embodiments, the processor of each gaming device is designed to transmit and receive events, messages, commands or any other suitable data or signal between the individual gaming device and the central server. The gaming device processor is operable to execute such communicated events, messages or commands in conjunction with the operation of the gaming device. Moreover, the processor of the central server is designed to transmit and receive events, messages, commands or any other suitable data or signal between the central server and each of the individual gaming devices. The central server processor is operable to execute such communicated events, messages or commands in conjunction with the operation of the central server. It should be appreciated that one, more or each of the functions of the central controller as disclosed herein may be performed by one or more gaming device processors. It should be further appreciated that one, more or each of the functions of one or more gaming device processors as disclosed herein may be performed by the central controller. In one embodiment, the game outcome provided to the player is determined by a central server or controller and provided to the player at the gaming device. In this embodiment, each of a plurality of such gaming devices are in communication with the central server or controller. Upon a player initiating game play at one of the gaming devices, the initiated gaming device communicates a game outcome request to the central server or controller. In one embodiment, the central server or controller receives the game outcome request and randomly generates a game outcome for the primary game based on probability data. In another embodiment, the central server or controller randomly generates a game outcome for the secondary game based on probability data. In another embodiment, the central server or controller randomly generates a game outcome for both the primary game and the secondary game based on probability data. In this embodiment, the central server or controller is capable of storing and utilizing program code or other data similar to the processor and memory device of the gaming device. In an alternative embodiment, the central server or controller maintains one or more predetermined pools or sets of predetermined game outcomes. In this embodiment, the central server or controller receives the game outcome request and independently selects a predetermined game outcome from a set or pool of game outcomes. The central server or controller flags or marks the selected game outcome as used. Once a game outcome is flagged as used, it is prevented from further selection from the set or pool and cannot be selected by the central controller or server upon another wager. The provided game outcome can include a primary game outcome, a secondary game outcome, primary and secondary game outcomes, or a series of game outcomes such as free games. 9 The central server or controller communicates the generated or selected game outcome to the initiated gaming device. The gaming device receives the generated or selected game outcome and provides the game outcome to the player. In an alternative embodiment, how the generated or selected game outcome is to be presented or displayed to the player, such as a reel symbol combination of a slot machine or a hand of cards dealt in a card game, is also determined by the central server or controller and communicated to the initiated gaming device to be presented or displayed to the player. Central production or control can assist a gaming establishment or other entity in maintaining appropriate records, controlling gaming, reducing and preventing cheating or electronic or other errors, reducing or eliminating win-loss volatility and the like. In a further embodiment of the invention as shown in Figure 2, the ticket reader system is considered separate to the gaming machine. This may be in the case of retrofitting existing gaming machines or may be due to regulatory requirements in some jurisdictions. In these embodiments, the ticket reader system processor 201 is connected to an in communication with the processor 12 of the gaming machine. A ticket reader and acceptor 202, display device 203, sound card 204 and speakers 205 are all connected to an in communication with the system processor 201 to provide the required functionality. In a use, a player decides which gaming machine they wish to play and inserts their player card having player information into the machine. The player then inserts credit, preferably in the form of a ticket into the gaming machine. The gaming machine is in communication with the central server which stores player information and informs the central server that the player has inserted their player card and a ticket having credit into the gaming machine. The central server validates the player information and ticket as required according to legislation or internal controls and then determines whether bonus credit is to be allocated to the player. The allocation of bonus credit is given in accordance with promotional activities that the venue runs for members. In this way the venue can reward members who are currently gaming by providing them not only with rewards points but also with an allocation of credit onto their credit meter. That is, the player can be allocated additional credit directly to the gaming machine that they are playing. As discussed above, the venue may have a number of promotional activities running simultaneously. The activities may be well publicised to allow players to take full advantage thereof. In one such promotional all registered players receive a bonus credit of $15 per day on their first gaming machine play (when they first insert their credit). The bonus credit may be capped according to the rules and preferences of the venue at, say, $100 or $50 or $30 or $15 according to the preferences. For example, if the bonus credit is capped at $15 per day, even if a player inserted credit of $100 into the gaming machine they would only receive $15 bonus credit. In other embodiments there is no cap on the bonus credit awarded. 10 As an example, if a player inserts $15 into a gaming machine, the central gaming server can double the credit to $30. This bonus allocation of credit would be for gaming purposes only and could not be transferred onto a standard ticket in ticket out (TITO) ticket, however, the win from that game play could be transferred onto a ticket. It can only be utilised through playing the machine. As such the member obtains additional play from the machine. The preferred embodiment of the invention allows gaming customers to be directly rewarded during their gaming activity. This is an improvement of existing indirect and informal mechanisms of providing point and able to be spent money in the venue monetary rewards. It does not encourage players to increase they gaming bet and it may reduce the player's need to spend their own money because it is artificially extending the worth of their gaming dollar. Figure 3 shows a flow chart according to the preferred embodiment of the invention. At 301 a player approaches the chosen gaming machine and inserts their player card and credit ticket into the machine. This information is transmitted to the central server which determines whether a promotion is currently active and whether any bonus or promotional credit is to be awarded to the player. If no promotion is active and no bonus credit it to be awarded the credit meter on the gaming machine simply displays the credit that was inserted into the machine by the player as shown in 302. For example, if the player inserts a ticket containing $15 into the gaming machine then the credit meter shows $15 and $15 is available by the player to wager on the gaming machine. If a promotion is active and bonus credit is to be awarded to the player then the process continues to 303 where the appropriate bonus credit is allocated to the credit meter of the gaming machine in conjunction with the credit inserted. For example, if the player inserts a ticket containing $15 into the gaming machine and a promotion doubling all inserted credit is active then an additional $15 of bonus will be awarded to the player and the credit meter on the gaming machine will show $30 which is available to the player to wager on the gaming machine. Any commercial processor may be used to implement the embodiments of the invention either as a single processor, serial or parallel set of processors in the system. Examples of commercial processors include, but are not limited to MercedTM, PentiumTM, Pentium JITM, XeonTM, CeleronTM, Pentium ProTM, EfficeonTM, Athlon, AMD, Intel CentrinoTM, Intel Core DuoTM, Intel Core 2 DuoTM, Intel CentrinoTM, Intel XeonTM and the like. Display screens may be segment display screen, analogue display screens, digital display screens, CRTs, LED screens, Plasma screens, liquid crystal diode screens, and the like. Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. 11