Proposal B: Derived mesh and elemnt classes for domain decomposition approach (Do not merge)

To  @norihiro-w  @rinkk @TomFischer :

Contrary to proposal A (#420),  class Element has also been derived with additional data member for active node indices, this is demonstrated in another  PR. With later local  ``#ifdef`` is avoid, but an index mapping to access element nodes is required, e.g.,
```
for(unsigned i=0; i < elem->getNNodes(); i++)
{ 
   Node *node =  elem->getNode(elem->getLocalActiveNodeID(i));
}
```
The node index mapping, elem->getLocalActiveNodeID(i) may slightly slow down the computation than use compiler oriented preprocessor.