Fix some minor inconsistencies and inefficiencies:

Fix some minor inconsistencies and inefficiencies:

- no extra nodes are created at all if the material has no random
  objects defined

- the range selector is place correctly under the transformation

- there is only one range selector for each object type in each
  triangle (experimental -- doesn't seem to make a difference in speed
  or memory)

This patch removes Curt's patch that randomized ranges slightly, since
individual random objects no longer have their own range selectors.
It also leaves the object-group-range value unused, for now.