Factored out usage of Rectangle

Factored out usage of Rectangle

- Factored out usage of Rectangle throughout the engine, instead using
lighter-weight Rect2D.

- Removed GraphicDrawer's deprecated use of QUADS.

- Factored out IWindowManager as a service. No provided through the
Game.

- Delegated responsibility of updating the window manager to the
provider (Whoever implements the abstract method getWindowManager)
rendering\input of it is still handled by the Game class.

Jeremy. Allen. Wildsmith