Adjust the shadow shader to prevent seeing shadows on the opposite sides of
objects.  Closes #2544.
Use the "correct" shadow strategy: include only ambient term when in shadow.
Merge branch 'master' of https://github.com/highfidelity/hifi
Fix for avatar LOD's getting into a degenerate state.  Don't persist the
avatar LOD, since we adjust it more rapidly.
Make sure we process the model root nodes in alphabetic order.
Make sure we reset our LOD adjustments before we switch back from throttling
the renderer.
Merge pull request #2556 from ey6es/master

Fix for shadows' showing up on the wrong side of objects.