Various major improvements to the engine

Added per frame animation callback methods. Improved camera rotation.
Added camera blend states. Added support for camera render target
shaders. Converted default fonts to bitmap fonts. Added support for
loading states in the background while a "loading" state is running.
Expanded debug info. Added dynamic quadtrees for improved performance
and reduced garbage collection. Removed the members overlay system to
prevent ambiguity between overlay and non-overlay members of the same
group. Dramatically improved collision detection/response speed.
Utilized the GenTimer class for features such as sprite flicker, camera
fades, camera flashes, sound fades, etc. States manage their own
cameras. States can be switched out and loaded again from where they
left off. Tilemap drawing bounds accommodate for camera rotation. Added
ablility to dynamically add or remove tilemap tiles, and any automatic
tilesheet will adjust accordingly. Added support for any amount of
colors to be interpolated for progress bars or emitter particles. Added
background music manager. And various other improvements.