We are using stuff from there.

[[Imported from SVN: r9880]]

[[Imported from SVN: r9844]]

[[Imported from SVN: r9840]]

[[Imported from SVN: r9767]]

For a general grid, such loops are only possible for codimensions 0
and the grid dimension.

[[Imported from SVN: r9766]]

[[Imported from SVN: r9764]]

[[Imported from SVN: r9763]]

GlobalP2Mapper is intended to be for P2 finite element spaces, what
GlobalIndex is for P1 spaces: a numbering for all degrees of freedom
that is globally unique across all processors.

[[Imported from SVN: r9761]]

Iterators over entities are only mandatory for vertices and elements.
But here the user may also request indices for other entities.
Hence one cannot use a straight iterator.

[[Imported from SVN: r9759]]

No idea why valgrind didn't complain about this.

[[Imported from SVN: r9758]]

[[Imported from SVN: r9749]]

And use it in one place in VectorCommunicator

[[Imported from SVN: r9748]]

[[Imported from SVN: r9747]]

[[Imported from SVN: r9746]]

[[Imported from SVN: r9744]]

Much easier to use than the previous API.

[[Imported from SVN: r9735]]

[[Imported from SVN: r9733]]

[[Imported from SVN: r9732]]

Those do many-to-one communication with a single method call.
Previously, two subsequent calls were needed.  There is no reason
why the interface has to consist of two calls.  A single one is
much easier to use.

[[Imported from SVN: r9730]]

That way we can handle multigrid transfer matrices as well.

[[Imported from SVN: r9719]]

The globalindex.hh and uniqueentitypartition.hh is from Benedikt Oswald.
The rest is from Benjamin Bykowski, with a few fixes from me.

The globalindex stuff should go into dune-grid eventually, but it needs
some polishing first.

[[Imported from SVN: r9718]]