Window & State/Scene handling

[numpad]

Add a wrapper around the base window. Abstract settings, initialization and the gameloop into it. Support for gamestates/scenes is also required to cleanly work with menu, settings, core game and so on, think of something to work with it as flexible as possible. (Pause scene overlaps the game, transition between menu > start game and the game, ...)

• Basic window abstraction
• Window handling
• Scene Management