RBCs collect & manage gloms; all die from whites.

New tags and layers.
Re-parent collided glommers under RBC xform.
RBCs collect child glommers in a List.
Move glimmer to RBC layer, to avoid being stolen by other RBCs.
Rigid body physics take over when RBC collides glommer.
RBC OnDestroy calls Destroy on child glommers.
Destroy RBC and glommers on collision with WBC.
Comment out unused field in Warpable.