- Updated MTLLoader.parse signature
- Shifted MaterialCreator to an inner class MTLLoader.MaterialCreator, aligning with actual Javascript
- Added MaterialCreator.crossOrigin
- Corrected MaterialCreator.setCrossOrigin parameter type

Almost all models that use occlusionTexture use texCoord 0 - the loader
prints a console message for each material for such models which seems
redundant / excessive.

However, if other textures use texCoord that's not 0, the resulting
texture will not be rendered properly. We now detect this case and issue
a warning.

This fix creates all uv channels, not only the first one

- Removes GeometryUtils random point selection.
- Adds MeshSurfaceSampler for incremental, weighted surface sampling.
- Adds 'webgl / instancing / scatter' example with InstancedMesh.
- Adds 'Flower.glb' sample for the example.