Allow copying of AbstractVolume
The copy constructor was deleted, but I don't really see a reason why. I ran into this during the ATLAS Calo construction, and unless there's a good reason why they shouldn't be copyable, I think we should make them.
The copy constructor was deleted, but I don't really see a reason why. I ran into this during the ATLAS Calo construction, and unless there's a good reason why they shouldn't be copyable, I think we should make them.