* New webgl_physics_brick demo. Cutting a convex by a plane works, but it must be refactored to work from Geometry, not from "segmentedobject"

* webgl_physics_brick: Splitting a convex mesh with a plane works.

* webgl_physics_brick: Preparing to refactor objects

* webgl_physics_brick: Refactored objects to hang on the THREE.Object3d

* webgl_physics_brick: Radial subdivision works. To do: non-radial one.

* webgl_physics_brick: Non-radial subdivision works.

* 'breaking things' example works.

* added webgl_physics_convex_break to example index. Aded a pyramid.

* webgl_physics_convex_break: Add friction

* webgl_physics_convex_break: Add velocity and angular vel. from parent.

* webgl_physics_convex_break: Change guideline comment.

* webgl_physics_convex_break: Changed page title.

In the previous commit there were still situations where export
selected would not work properly.

- Fixing Export Selected: Removed most of the calls to ls() which does
a physical select which would really mess up the attempts to Export
Selected. In place I am using listHistory followed by listConnections
which seems to work correctly.
- Updated references to "Diffuse" in maya to be "Color" which is what
was actually being used. Added comments about this to the README.
- Changed code reference of "diffuse" to "color" where it was
appropriate for clarity.
- Added code that keeps it from exporting bones/animations on Export
Selected because it currently doesn't work. Also added Note in the
export dialog to this effect.
- Fixed how opacity was exported. Previously was grabbing the A channel
of the RGB object, but Maya stores transparency in all three RGB
channels. Grabbing R channel for opacity value in JSON.
- Added comment regarding the JSON exporter hack at the bottom of the
file for clarity.
- Turned on Pretty Output by default. I saw no reason not to now that
I've cleaned up the output.
- Removed depreciated arguments from the frameLayout call in MEL. -bs
is no longer supported.
- Moved the bones checkbox and related textfield into the animation
section. Seemed logical.

* Fix Matrix3 Matrix4 getInverse throwOnDegenerate

* Update throwOnDegenerate assertion

* Serialize and load JSON Light .shadow property

* Add .toJSON() method to LightShadow
* Light .toJSON() writes .shadow property
* Parse .shadow property in DirectionLight and Spotlight JSON data

* Remove .castShadow condition when exporting .shadow property to JSON

I’ve added a handful of improvements that I think will really help
people trying to use Maya with 3JS:

1. The current plugin will only perform an “EXPORT ALL” regardless of
what you select from the menu in Maya. I have fixed that so you can now
“Export All” or “Export Selected”. Export all sill merges geometry
rather than exporting a 3JS scene, may fix that in the future.
2. Updated the default extension to be “.json” rather than “.js”. This
is more in-line with 3JS and the other exporters.
3. I pulled the JSON encoder from the Blender exporter and integrated
it into the Maya one so that each item in the ups, faces, vertices, etc
arrays are no longer on a separate line. Makes the file MUCH easier to
read and debug.
4. Turned off sorting of the JSON output. This is more of an opinion,
but I didn’t feel like it helped the output at all.