Fix bugs in MElement::xyz2uvw and in dgShellPartDomain

Fix PETSc deprecated warnings (since PETSc 3.6 / 3.7)
Fix BCs containers and their groupOfElement destruction --> need c++11
(cm3)
Update CMakeLists (cm3) to support c++11
Fix cm3 tests, and remove import scipy as unused (+ python3 support)
Fix DLOPEN warning for msch project