This is needed to build with a recent dune-common and dune-fufem

The CI system found this for me, because it only goes wrong
when dune-foamgrid is not available.

I want the interpolation rule to appear in the log files.
It is to easy to use the wrong one by accident.

Otherwise certain matrix-copying methods will not work anymore.

Makes the code a bit shorter and easier to read.

Make them a parameter instead.  This allows to switch more easily between
geodesic finite elements and projected finite elements.

Otherwise, the ParaView 'glyph' filter won't recognize the direction fields.

Such measurements are now centralized in the program compute-disc-error.cc.

It is still no function in the dune-functions sense, but at least the
basis parameter needs to be a dune-functions basis now, rather than
a deprecated dune-fufem basis.

And make that code path work again!

Unfortunately, this bases needs to be switched on and off using preprocessor
commands.  Hopefully I'll find a way to make that prettier in the future.

That really was a hack: the build system should do it.

[[Imported from SVN: r10111]]

[[Imported from SVN: r10103]]

[[Imported from SVN: r10096]]

[[Imported from SVN: r10083]]

Conceptually cleaner, and makes for simpler code.  Most importantly, we will want
to pass the Basis::LocalView to the local assemblers.  For that we need the actual
basis, not just the grid view and local finite element.

[[Imported from SVN: r10082]]

[[Imported from SVN: r10081]]

At least the harmonicmaps.cc example still works as before.
[caveat: only tested without HAVE_MPI]
Internally, at various places in the code, a dune-fufem basis is still constructed
from the dune-functions one.  These parts can be ported one by one, as dune-fufem
slowly replaces its own bases by the ones from dune-functions.

[[Imported from SVN: r10080]]