Added btMultiBodyPoint2Point, it can be used between btMultiBody vs btMultiBody or btMultiBody vs btRigidBody
Allow picking of btMultiBody, using a btMultiBodyPoint2Point constraint, with limited strength to avoid adding too much energy to the system (= blowup)
Add btMultiBodyJointMotor, it can be used in combination with joint limit (just add the joint limit after the motor, to avoid jitter)


git-svn-id: http://bullet.googlecode.com/svn@2682 08e121b0-ae19-0410-a57b-3be3395fd4fd