WebGLUniforms: Add unsigned vector array support for uniform.

[SuperSodaSea]

Description

Writing unsigned vector uniforms in shaders:

uniform uvec2 foo;

And using them can result in this exception:

TypeError: u.setValue is not a function

I checked out the code, and found that the WebGLUniforms didn't take care of UNSIGNED_INT_VEC2/3/4. This pull request add code to support them.

[WestLangley]

@Mugen87 FYI, I added the missing milestone.

[mrdoob]

Thanks!