Worked more on resources, shaders, and other things.
GameState class will now call enable, disable, update and draw methods on its components when needed.
Changes to game state classes.

Made IGameState inherit directly from IDrawable and IUpdatable instead, a
game state shouldn't be considered a component that can be added to other
game states.
Removed Enabled, Enable(), and Disable() from IGameState, they weren't
used.