Deep copies in AMG

I'm unsure whether this is a bug or a feature.

Currently several classes in the AMG perform expensive deep copies, in particular the hierarchy is always copied using a deep copy. This leads a full copy of the hierarchy when copying an AMG, FastAMG, TwoLevelSolver, ...

Is this intentional? Currently it is used in

• twolevelmethodtest.cc: there is an explicit test for the copy-constructor, but it is unclear what the intended behaviour is.
• pthreadamgtest.cc: Here a couple of AMGs are created from a single initial instance. After the copy several objects are set to other values so that I would assume that the other ones can be shared. But the there would be no need for a deep copy as we set the other ones anyway.
• pthreadtwoleveltest.cc: the same...