Fix imagebitmap example

Updated example to show performance improvement

Create Texture.html

Implementing support for ImageBitmap

Update envmap_fragment.glsl

ColladaLoader2: Refactoring multi material support

Per https://github.com/mrdoob/three.js/issues/11505#issuecomment-308270666
Clarifying properties that only apply under certain conditions.  Also adding a common-sense note regarding repeat settings, since Clamp tends to be the Wrap method default and that does affect Repeat behavior.

Per https://github.com/mrdoob/three.js/issues/11367#issuecomment-308303716
Equirectangular U sampling update to intuitively equiangular-per-raster sampling.

A quick visual test shows no change from the old version, which worries me a bit, since I'm not getting the trig-on-paper to give identical results.  If the math DOES work out provably identically, the original version is certainly more efficient.

Support wrap mode of texture in FBXLoader

add getRenderLists() method to WebGLRenderer

VelocityNode update (Flaccidity Map)

clock.stop should set autoStart false

ColladaLoader2: Added multi material support

[gltf] Use opaque alpha mode by default.

ColladaLoader2: Added missing var