Ken McClure:  Update to scene.dae.  removed rover tracks from scene file.  Adding in separated models for curved and straight rover tracks.
Added roverTracks node to environment
Ken McClure:  Update to straight rover tracks
Aligned tracks with graph line.
Merge pull request #158 from virtual-world-framework/Ken-Art

Ken McClure:  Update to scene.dae.  removed rover tracks from scene file...