[[Imported from SVN: r9975]]

Normally, the two different level grid views.  Previously we used the same one
to compute the localToGlobal renumbering for boths rows and columns.  Of course
that screws up the numbering.

I am not quite sure when that got introduced.  I may have gotten in fairly recently,
after the upstreaming of the GlobalIndexSet classs.

[[Imported from SVN: r9962]]

[[Imported from SVN: r9961]]

[[Imported from SVN: r9956]]

[[Imported from SVN: r9954]]

[[Imported from SVN: r9935]]

In particular this means having to carry mappers for the local indices around.
This makes the code more verbose, but it also makes it easier to see what is
happening.  While coding this stuff I keep having doubts about whether all
the renumbering works correctly...

[[Imported from SVN: r9925]]

The local copy was to get the thing developed and working.  Now that it is
working we upstream it into dune-grid.

[[Imported from SVN: r9922]]

The IndexSet interface class from dune-grid doesn't have it, and we want
to be like the interface method as much as possible.

[[Imported from SVN: r9921]]

[[Imported from SVN: r9920]]

That's what this method is called in the dune-grid IndexSet
interface.

[[Imported from SVN: r9919]]

Yes it is to be moved to dune-grid, but for the transition it is
easier to use the one from this module.

[[Imported from SVN: r9916]]

[[Imported from SVN: r9902]]

[[Imported from SVN: r9763]]

Much easier to use than the previous API.

[[Imported from SVN: r9735]]

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]]