Partial Sprite Overhaul

Added the Sprite, MoveableSprite, AttackSprite, and ShooterSprite, and
partially implemented them. I plan on adding more sprites of generic
type, but thats all for now. Also, added a SpriteController class, which
in a sandbox-environment, keeps track of all the sprites to be
processed, handles collision detection,  and updating, drawing, and
maintaining unique ids for all sprites to be processed within that
screen.