BulletSim: remove the unused RestoreBodyDependencies used by linksets
and vehicles and clean up code by removing their kludgyness.
BulletSim: fix build break introduced by previous commit
BulletSim: working on COM
BulletSim: center-of-gravity linkset changes. Not working yet.

Conflicts:

	OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
BulletSim: small change to center-of-mass computation left out last commit
BulletSim: remove setting of vehicle InterpolationRotationalVelocity.
This doesn't seem to help the vehicle stability.
Rename vehicle internal variables adding a "V" or "W" so it is clear
when coordinates are vehicle or world relative.