Remove unnecessary comme, add semicolon and remove duplicate semicolon in webgl_materials_envmaps_hdr

* Examples: use .texture of input render targets.

* Assign null instead of undefined.

* fix bug where gammaInput/gammaOutput were reset by the PMREM generators.

# Conflicts:
#	examples/js/pmrem/PMREMCubeUVPacker.js

* propagate encodings properly between PMREM CubeUVPacker and PMREMGenerator as well as through texture constructors.

# Conflicts:
#	examples/js/pmrem/PMREMCubeUVPacker.js

* turn off tonemapping, fix None HDR map option.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* minor envmaps_hdr improvements.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* fix double decode.

* recalc materials when changing texture encodings.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* clean up envmap_hdr example.

float and half HDR CUbe Maps load and are properly generated.  Something wrong when using RGBE encoding.

cube_uv_reflection map shader.  (written by @spidersharma03, modified by @bhouston)