improve comments and cleanup code related to model animation
improve comments and cleanup code related to model animation

JohnRThomas/opengl-examples,JohnRThomas/opengl-examples,JohnRThomas/opengl-examples,runewake2/opengl-examples,runewake2/opengl-examples,JohnRThomas/opengl-examples,runewake2/opengl-examples,runewake2/opengl-examples