Simple Test on 2D Grid. Call to PartMeshKway causes segmentation fault.
"elmdist" is supposed to be an array of size "processes+1".
"eptr" and "eind" arrays got confused.
Asking for rank zero doesn't make any sense here.
Setting environment variables not necessary.
Call PartMeshKway just on process zero with local Communicator.
Appears to work, but resulting partition looks suboptimal.
Added GlobalUniqueIndex class and small test code for outputting global indices after computing an initial partitioning.
"elmdist" should contain number of elements, not number of nodes.
Add some preprocessor magic to also build with ParMetis 3.x

Signed-off-by: Convex Function <329364@gehry.mathepool.rwth-aachen.de>
Exported ParMETIS related code into a separate class.
Remove unused update method. Add getter for indexOffset.