Improve performances of countValidVoteWithConstraint/sumValidVoteWithConstraint

| Q                   | A
| --------------------| ---------------
| Type                | Suggestion
| Condorcet version   | 4.2


Can be useful for very big elections. Especially since the Console version print that. Can be very slow with an external data Handler (parse every vote).

Can be done with a cache on VotesManager, like done for `countVotes()`?