This patch fixes various bugs in the non-pdelab implementation:
1. The index sets are now correctly setup.
2. For the box model it is made sure that the right hand side is
consistent.

Now the test_box1pwithamg converges in the same number of steps of
the non-linear solve in parallel as in serial. (Not the case with
pdelab!)


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/branches/strip-pdelab@13252 2fb0f335-1f38-0410-981e-8018bf24f1b0