internal/Graphics: Add ShadowState struct
Make shader variable definitions internal

Move the #defines into the internal/Graphics header. This cripples
test/device since it doesn't use a Camera object, but instead manually
sets projection and perspective uniforms. This can easily be fixed
in the future.

All source files which need to fetch variable locations now include
the internal/Graphics header to have access to those variable names.

Once the GL shadow state is working this will most likely not be needed
except internally for the internal functions which retrieve current
state information.

Conflicts:
	include/bakge/internal/Graphics.h