* Set renderer to correct resolution when entering VR mode

This ensures that the scene always renders with the best resolution for
the HMD in use. (Will get a 1:1 pixel ratio) For performance reasons
developers may want to render at a lower than recommended resolution. To
do so set VREffect.bufferScale to a lower values (like 0.75).

Will restore the renderer to the previously set resolution when the user
exits VR mode.

* Removed bufferScale from previous VREffect change

* Matrix4: added preMultiply method

* Matri4: preMultiply -> premultiply

* 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.

Set to use HAVE_CURRENT_DATA for VideoTexture updates

Greater than or equal to readyState HAVE_CURRENT_DATA

Video texture should check ready state of video to see if current frame is renderable, not if future frames are renderable

Added 2 New SpotLight Examples

Seems it made sense to add the Extra Examples after the Code Example, but maybe that needs rethinking?

This adds the single spot light example into the SpotLightHelper doc

Embedded Single SpotLight iframe example into SpotLight.html doc

Well I guess it's more Magenta Yellow and Cyan

I changed to this description well "A point light that can cast a shadow in one direction with a falloff cone."
I put the examples at the top since they are most relevant.

If you control-click the target object is set to white (click randomizes color without CTRL).

Random color set when clicked but control-click sets the target object to white.

randomColor function checks for a material or if it's a property (of a mesh).

Thanks for the peer review, and insights.

Thanks for the peer review, all excellent points.

webgl_terrain_dynamic: bugfixing and simplification

Using context's max attributes number

adds both new spotlight examples

This adds second example with 3 animated spotlights converging.

Anaglyph: Fixed transposed color matrices.

Fixed test for Matrix3.getInverse.