Support for separate alpha map textures.

Added support for using a separate alpha map with MeshBasicMaterial, MeshLambertMaterial, and MeshPhongMaterial, and updated the OBJ converter to set materials as transparent if an alpha map is defined.
Moved "alphamap_fragment" shader chunks immediately after "map_fragment".

This ensures proper alpha testing and avoids other potential issues with deferring alpha map blending until late in the fragment shader.
Use the green channel from alpha maps instead of red.

More precision is used for the green channel in RGB565 and DXT texture formats, so this would improve the quality in those cases.
add glsl changes
This just annoyed me
Merge pull request #5013 from gero3/patch-25

Make use of [] instead of new Array()
WebGLRenderer: These may avoid light to be black but also create hard to understand webgl errors.
Merge branch 'dev' of https://github.com/mrdoob/three.js into dev
Updated builds.
Merge pull request #5010 from gero3/glslBuilder

add glsl changes
Shader fixes and build.py clean up.
Renderer Plugin to handle stereo rendering and head tracking for VR HMDs. It uses the native Firefox API
Making requested changes after review
Removing VRPLugin.js
Adding comments
Merge branch 'dev' into patch-3

Conflicts:
	src/renderers/shaders/ShaderChunk.js
Added alpha map fragment shader sources to the build includes.
Update webgl_camera.html, removing container div

Container div is unnecessary since it's created in init() function as an appendChild() to body.
Updated builds.
Merge branch 'patch-1' of https://github.com/bloublou2014/three.js into dev