used to move data during load balancing. The dune-fem DofManager has been adjusted
accordingly.

- instead of #ifndef NDEBUG
  now use #ifdef ALUGRIDDEBUG
- istead of assert( cond );
  now use alugrid_assert ( cond );
  (from dune/alugrid/common/alugrid_assert.hh)
So instead of having to define NDEBUG to avoid debug code being executed
(improves performance by 60%) one always avoids debug code as long as
ALUGRIDDEBUG has not been define.

  MPI_Comm --> ALUGridMPIComm
  No_Comm  --> ALUGridNoComm

Now the library compilation yields always the same result, independent of HAVE_MPI.
Also, almost all ALU3DGRID_PARALLEL could have been removed.
From now on, there should be no .cc file containing ALU3DGRID_PARALLEL or HAVE_MPI.
Otherwise it must be an inline header file.