MeshBuilder: create primgroups as controlled by the grouping stream
MeshBuilder: create primgroups as controlled by the grouping stream

zenmumbler/libzm,stardazed/stardazed-tx,zenmumbler/stardazed-tx,stardazed/stardazed,stardazed/stardazed,zenmumbler/stardazed-tx,zenmumbler/libzm,stardazed/stardazed-tx,stardazed/stardazed-tx,zenmumbler/libzm,zenmumbler/stardazed-tx,zenmumbler/stardazed-tx,zenmumbler/libzm