Add ability to swap shaders with 'p' key.
Move ModelView initialization into sceneParser.

Should have done this a long time ago..
Keep a references to camera on each object
Add cel_shading reference. Currently just phong.
Fix bug in camera movement.
Discratize diffuse lighting for cel shader.
Change specular the color white, add silhouetts.
Minor changes to discratization and silhouettes.