Created a whole backend

* Scene hadling
   To be able to handle different levels, show menus, intro screen
   and stuff, a scene handling was introduced first.  It contains
   a scene interface and a scene manager.  The scene manager activates
   a scene and redirects the events (render, step, etc) to the active
   scene.

* Living and Player handling
   A class Living was introduced which is represents any dynamic elements
   in the game.  The player is a subclass of Living.

* Input handlingj
   A schene MoveAroundSchene was introduced which also handles the input
   for the player.