SubEntity::setMaterialName enhancement

[bishopnator]

If input material name is same as current mMaterialName, method should return immediately - getByName method is not very fast for runtime.
I am changing materials on entities per frame and this method slow donw my performance due to this call. I suppose that testing should be part of this method.

[sinbad]

Ok, will add early-outs to all occurrences.