OpenGL Hygiene

All functions in the graphics package satisfy one of the following properties:

1. They do not change OpenGL state, and there is a unit test certifying this in the same folder as the function definition.
2. They make a change to OpenGL state, and there is a comment at the function definition elaborating how OpenGL state is changed as a result of the function. There is also a unit test certifying that the documented change is the only one made.