This broke tons of examples on Chrome/Android...

This patch modifies WebGLRenderer to take in an existing WebGL context, and adds an unit test to test the behaviour.
Signed-off-by: NPrabindh Sundareson <prabindh@yahoo.com>

Values are now mandatory. This should avoid corner dpr cases.

WebGLRenderer: Added clearColor, clearDepth and clearStencil. See discussion in ef7ead99.

WebGL itself has it set to true by default, but I have the feeling alpha is not needed in most of the cases. Plus we save memory and increase performance.

This commit fixes a skinning bug that occurs when two or more SkinnedMesh objects share a common material and have bone textures of different sizes.  Currently, bone texture sizes are hard coded into the shader program, requiring the program to be re-built when the bone texture size changes; however, the current implementation does not handle this correctly, which can lead to the shader accessing incorrect bone transforms.

This commit uses two uniforms to store the bone texture dimensions.  These uniforms are updated as needed, eliminating the need to re-build the shader and fixing the bug.

Simpler check for colors in geometry. As suggested by @WestLangley in af042be6.

If attributes are used by a shader but not supplied in the data, default
values can be assigned.
When a shader is created, default values for "color", "uv" and "uv2" are
automatically created.

It was a hack for ro.me...