WebGLPrograms: Cache isWebGL2, logarithmicDepthBuffer, floatVertexTextures, precision, maxVertexUniforms, vertexTextures.

Fix the case where there are two objects with the same material in the scene and one has receiveShadow=true and the other has receiveShadow=false.

This also prevents possible extra shader compiles when the same material is reused with receiveShadow enabled or disabled in the same scene.

Created a separate variable for cc normal, independent perturb implementations

Only shadow casting lights now get entries in the shadow maps arrays in shaders. Lights are sorted so that shadow casting lights come first, so the index of the light in the shadow maps array still matches the index in the normal light data array.

This conserves texture slots, enabling to use more lights in scenes where shadow maps are enabled. Uniform update performance and shader execution performance should also be a bit better when there's a mix of shadow casting and non-shadowed lights.