BulletSim: remove unused MaxTaintsToProcessPerStep parameter
Have SOP and LSL_Api call the proper GetCenterOfMass and GetGeometricCenter
routines on the physics engine. Won't make a difference for any
existing scripts since ODE always returned Vector3.Zero.
BulletSim: allow changing position and rotation of a child of a linkset
without rebuilding the whole compound shape. Should make vehicles move
smoother.