First person view added

I added a first person camera, so now the Tab button alternates between complete top down view, closer top down view and first person view. In first person view the controls are also switched to  simple tank-like FPS controls - no strafing.

I also added ceiling tiles that are only visible in first person view. 

Most of the assets are not made to be viewed up close, but  the Tiles and Big Tiles generated levels do look quite nice in my opinion. The Markov forest (3rd setting), too.