[AnimationClip] animating sprites

! doesn’t work yet

+ animation clip knows about ptr curves
+ converter for sprite curves
+ objects named only by their Z (no filename attached any more)
+ sprite renderer can give you it’s current sprite
[CurveCalcSprite] fixes

+ properly exporting changes in sprites
[PrefabMaker] fixed animation bugs

+ z-sorting bug solved, instead of using SortingOrder we’re just using
Z position again, but mulitplied by 10 to get values of like 0.1, 0.2.
this seems to solve z-fighting problem and fixes animations
+ removed unity crabby example, as it requires now crabby sprites to be
imported into unity to work. use is as an example project now