Decoupled grid adaptive models can now use the restart function

   - writes *.grs files which store the macro grid and the refinement
   - so far, only ALUGrid provides implementations for writing and
     reading grids -> adaptive restart can only be used with ALUGrid
   - reviewed by Bernd



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@10690 2fb0f335-1f38-0410-981e-8018bf24f1b0