small errors in Arh3Reader/ rh3Writer corrected and ProblemStat::initialize modified to allow bahavior as in previous versions, for expressions::functors a degree mapper was added and the BlockMapper now is initialized with the correct number of components

Error in MeshDistributer corrected due to the use of non-initialized dofComm that is replaced by dofComms

merge of trunk with arhfile2 branch: 'using namespace' removed from header files, file readers/writer moved to subnamespace AMDiS::io, test for arh2writer added

Ups, mal ein code refactoring dass nicht gleich in 100 bugfixes enden. So, nun sollte der ganze parallele spass auch fuer gekoppelte Probleme ohne Tricks funktionieren. Nur testen will es mal wieder keiner, daher geh ich mittag essen.

DOFVector are named by init file, and VTK writer uses this information to name components of vtu files.