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)

Demos/OpenGL/DemoApplication.h

@@ -57,6 +57,9 @@ protected:
 
 	virtual void removePickingConstraint();
 
+	virtual void pickObject(const btVector3& pickPos, const class btCollisionObject* hitObj);
+
+
 	btCollisionShape*	m_shootBoxShape;
 
 	float	m_cameraDistance;