BulletSim: modify motors to return correction rather than current value
to better use them for incremental updates.
Modify prim and character to use the new motors.
Simplify the vehicle linear movement code to just update the velocity
directly or the basic movement.
BulletSim: small fix making sure terrain height is calculated
properly if the vehicle moves during vehicle actions.
BulletSim: fix problem of avatar sliding very slowly occasionally after stopping walking. Consolidate movement tests into the one prestep motion action
BulletSim: More aggressive as setting character velocity to zero
when should be standing.
Modify angular force routines to be the same pattern as linear force routines.
BulletSim vehicle turning is scaled like SL and is DIFFERENT THAN ODE!!
Fix some bugs in BSMotor dealing with the motor going to zero.
Add a bunch of parameters:  MaxLinearVelocity, MaxAngularVelocity,
MaxAddForceMagnitude, VehicleMaxLinearVelocity, VehicleMaxAngularVelocity,
and most of the values are defaulted to values that are larger
than in SL.
Use the new parameters in BSPrim, BSCharacter and BSDynamic.