move sprite transformations from spritesheet class to animation class

[ASong5]

i think moving the responsibility of performing sprite transformations to the animation class will allow for more consistently structured set of frames across all spritesheets (i.e., all set of frames would be a 2d list, rather than some having a third component to account for the transformed sprites; instead those would ideally be handled at runtime whenever necessary), thereby lessening the coupling that is currently present between various assets and their respective animations.