* Add PushEffect, handle effects in renderer
* Set effects instead of blend
* Stop using PushCompositeMode, use PushEffect
* Remove remaining composite mode things
* abstracted palettes, colors, and palette manager
* make asset manager use the palette manager interface
* added BGRA setter/getter, fixed lint errors
* abstraction for animation and animation manager
* Fixes#496 using ebiten.SubImage to Render Section of a Surface.
I had to add matching functions to both animation and sprite to get it to be called
for a sprite object.
* Fixed linter warning on comments for Sprite and Animation.
* Removing what's remaining of the old Sprite re-generation and caching.
