Better implementation for PhantomSprites

[jorisdormans]

We'll need four classes:
PhantomSprite: to keep sprite sheets in memory and to draw them to a graphics object.
PhantomSpriteRenderer: a renderable component that renders a frame of a PhantomSpriteSheet.
PhantomAnimatedSprite: inherited from PhantomSprite, but adds standard animation sequences
PahntomAnimatedSpriteRenderer: a renderable component that renders and animates based on a PhantomAnimatedSprite