more petsc solver usage
Enable MPI-parallelization in CMakeLists

Enable_MPI is set in add_dune_mpi_flags macro
Conflicts:
	CMakeLists.txt
last changes for petsc compat

Enable_MPI is set in add_dune_mpi_flags macro
Conflicts:
	CMakeLists.txt
use reserve with pattern for petsc matrices
post fem-update compile fixes