Animation Support in Models

* adds new properties to models to support animation:
   * animationURL - the url to an FBX file containing animation commands
   * animationIsPlaying - true/false is the animation playing
   * animationFrameIndex - used to skip to a frame
   * animationFPS - set the frames per second of the animation

* fixes FST based Models to "scale to fit" even if the FST file contains additional scaling info.

* moves Animation and AnimationCache classes to independent library so that it can be accessed by models and particles