Merged requested to merge fix/md-memoryleak-couplmanager-problem into master
The coupling manager had a shared_ptr to the problem and the problem to the coupling manager. This cyclic dependency leads to neither the problem nor the coupling manager being destroyed -> huge memory leaks.
fix embedded coupling managers
fix facet coupling managers
fix boundary coupling managers
check with valgrind that there are no memory leaks
Fixes #557 (closed).