Wrapper class for rigid body copies.
The RigidBodyCopyNotification class is a wrapper class for marshaling and unmarshaling rigid body copies. When receiving a copy notification a new shadow copy of the encapsulated body should be created. Copy notification must originate from the owner. The class template should be the collision system configuration and only serves the purpose to prevent compiler errors for specific collision system choices. The marshalling of the list of shadow copy holders can only be performed if the MPIRigidBodyTrait class is part of the rigid body class hierarchy, which is not the case for all collision systems. However, if it is not part of the class hierarchy then the function is also never called and the compiler need not compile the code and the template parameter prevents it.