Cleaned up/simplified construction of a btRigidBody

Fixed memoryleak in btOptimizedBvh (delete []m_contiguousNodes;)
Changed DemoApplication::localCreateRigidBody, so it adds the rigidbody to the btDynamicsWorld.
Added check for duplicate objects in world when adding.
Added assert to prevent setLinearVelocity on static rigidbodies
Added btCollisionFilterGroups to btBroadphaseProxy
removed duplicate 'btBroadphaseProxy*	m_broadphaseProxy;' in btRigidBody

src/LinearMath/btTransform.h

@@ -159,6 +159,13 @@ public:
 
 	btTransform operator*(const btTransform& t) const;
 
+	static btTransform	getIdentity()
+	{
+		btTransform tr;
+		tr.setIdentity();
+		return tr;
+	}
+	
 private:
 
 	btMatrix3x3 m_basis;