Merge pull request #1 from playcanvas/master

update from original
shaders
new shader system
now works on IE11, fixed some bugs, changed layers back to map transforms, cleaned code
added CPU directional light normalization to make lighting work correctly with new shaders
_minFilter -> minFilter
cleaned code
Merge pull request #47 from guycalledfrank/shader-system

Replacement shader system. Relaxes the limits on the number of lights, has better reflectance model, enables parallax mapping, includes gamma correction (off by default) and various other changes.