Merge branch 'parallel2d' of https://users.dune-project.org/repositories/projects/dune-alugrid into parallel2d

conected to every other process.

Also, enable HSFC for 2d grids.

We want to sort after correcting the element orientation,
because in the 2-3 grid the convention is, that it is oriented by
the orientation of the first inserted element.

added dimension == 2 to if-clause for recreateboundaryids as it basically reorientates the boundaroies