Cleanup
Added input in view and controller.

Input from the keyboard should now be caught by the view, read by controller and
sent to the model at every iteration of the game loop. The FPS-counter can be
turned on and off using the 'F' button, and consequently this input is not sent
to the model. Every check for specific buttons have to be hardcoded for now; we
might want to add something a little bit more extensible later (eg. model can
register what input it wants to get and associate them with certain callback
methods).