YaspGrid - reference implementation of the parallel grid interface

Finally the parallel grid interface, as we discussed it on the last DUNE Developer Meeting, is finished. There is a reference implementation in YaspGrid.

If you want to use the parallel interface you must have an MPI implementation available (automake can detect mpich and lam). To learn how to compile your DUNE project with MPI support have a look at dune-tutorial/Makefile.am.

Update: This last statement is outdated!