Two 'sgrid' functions when we only need one? #634
Description
As pointed out in PR #617, there are now two sgrid functions in the package: grid.py:sgrid and rlocus.py:_sgrid_func. It looks like _sgrid_func was removed in PR #193 (discrete omega-damping plot and tweaks by Sup3rGeo), but was re-introduced in PR #209 (sisotool and dynamic root locus zoom by icam0).