WebGLUniformsGroups: Fix programs sharing multiple ubo and support array uniforms

[RenaudRohlinger]

This PR fixes the fact that the UBO cache system was previously based per block and not per program which was breaking as soon as more than one UBO was used (wrong index). I updated the example by adding the lights UBO on the second material, to reproduce the issue just set back the old cache system in WebGLState.js:
uboBindings.get( program ) => uboBindings.get( uniformsGroup ) and you will see that the programs fail based randomly.

It seems that with multiple UBOs attached this change will trigger uniformBlockBinding per frame, I wonder about the performance implication of this call.

The PR also introduces the support for uniform array structure. For example:

struct PointLight {
	vec4 position;
	vec4 color;
};

layout(std140) uniform LightingData {
	PointLight pointLight[40];
};

Also, it might be interesting to add a note that it is necessary to only use vec4 with UBO and std140.

Most GPUs (Apple for example) do not render a correct result if a non-vec4 is being used when using a uniform array and std140.

[Mugen87]

Merging for further testing.