HALFLING: Add documentation to the HalflingEngine class
DEFERRED_SHADING_DEMO: Remove unneeded wireframe callback functions

Since they just set a value. Just use TwAddVarRW instead of TwAddVarCB
COMMON: Rename the methods of LightAnimators

Since they can do more than just translate
DEFERRED_SHADING_DEMO: Add documentation to the main app class