Basically finished the basic Paddle class to allow for PaddleController control.

Also commented basically everything except constructors, assignment operators, etc.
Added the first paddle controller, though not documented.
Made sure to clear the screen on every game loop iteration, otherwise rendering becomes additive.
Added width and height variables to the Paddle class and implemented setter and getter functions.
Added newlines to the end of src/EventState.cpp and src/EventState.h.
Documented all files in the src/GameStates folder and the MenuGameState class.

Also updated Doxyfile.in to search the new GameStates directory and the PaddleControllers directory.