[dune-fem] cmake for dune-fem.

[Robert Kloefkorn]

Hello dune-fem,

Stefan Girke and I work on the cmake support for dune-fem this week. I
have pushed the changes to the master branch now. It is not fully
functioning dues to some missing functionality in dune-common, but these
are only minor issues. To build the libraries and the tests mainly works
and we'll have to sort out the last problems along the way.

My overall conclusion is that the cmake build system is still in beta
state and I would currently not recommend to use it unless you are up
for some self-torture.

Best,

Rob