Added animation mapping to resource manager.
Resource manager is now accessible from a static method of the Game
class.
Interfaced updating of entities through the world class.
Interfaced rendering of entities through the world class.
Added methods to Animation and AnimationList to support rendering with a
Camera offset.
Fixed a bug in the Quadtree which caused a NPE when using the
BoundingBox constructor then calling reindex().
Fixed a bug which would cause a NPE if calling changeState() on a new
FSM which didn't have a previous state.

There's still some hardcoded stuff, but it should be somewhat more
organized now.