Fix material duplication with object duplicate

Current implementation of "deep copy" duplication of objects has an issue in that it generates copy of the materials. This is both unexpected from designer point of view as other 3D content creation tools don't do this, but also inefficient from the resource usage point of view that we then have a multiple copies of same material in the runtime environment (and also makes it harder for designers to find the correct material to edit from bunch of same materials). Initial fix is to instead use referenced materials in duplicate objects.

Proper fix for later releases is to have materials separate from objects (perhaps part of a UIP or maybe even UIA) and all objects reference materials. See QT3DS-1647.