A lot of changes, again I feel I should've committed sooner. Units have been restructured to use Interfaces to extend their functionality, this is opposed to having a distinct tree of Unit tiers with different functionality in each. The interfaces that were added are IDrawable.h, IDrawableImage.h, IPhysicsObject.h, and ICollidable.h. ICollidable.h is not fully implemented, but has several 'Colliders' built around the geometric classes. Units are now organized in two structures, the Scene class and its child Layer classes. Depth sorting is done each time a Unit is added or moved to the layers. A test has been set up in Arc Testing to show this off.