Clean up minor insanities in TestEngine and md2_viewer/Engine.  I was kinda sleep-deprived when I wrote this
Brought some of the input-handling code from the EngineInterfaces into the WindowManager class.

Mouse-movement is still handled by the EngineInterface because I have yet to even integrate it
into InputBinding.

Also, I need to re-implement the binding for md2_viewer's camera controls because the EngineInterface
was rendering the md2 models..  The solution to this will probably involve further minimizing the role
of the EngineInterface and moving this funcitonality elsewhere.  This fits with my eventual goal of getting
rid of the EngineInterface entirely.
There I fixed the keybinds thing.  EngineInterface binds the keys for WindowManager.
Currently the BIND_END constant is the only thing that prevents the WindowManager's
key binds from colliding with the EngineInterface's key binds.  In the future, I may
consider using strings to identifiy key binds instead.  This will be a much more readable
way to prevent collisions and it will also make it much easier to have 3 or more entities
all creating keybinds.