Even bigger commit...

AsteroidManager is now in a near-complete state, added some properties
to Camera, added an offset calculator in GameObject along with fixing
the RotationToVector method (X/Y mixup), added another useful method to
InputHandler (WasKeyDown), added a velocity inheritance option to
ParticleEmitter, added better draw depth settings, added a ton of
constants and objects to the Player class, re-fixed the ship sprite, and
prettied up some of the code.