no more using bs SYMMETRIC_DIFFUSION define in problems
[cmake] find petsc routines
[ms|fem] switch discretefuntion/matrix/solver types to petsc backend
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
per problem boundary type selection
preconditoner type from config
added dirichletconstrinats class from fem-poisson module
modify the copied dirichlet constraints class for our use
saves code by directly using parameter values to select the right petsc solver type

note bi_cg_stab -> bcgs
fixes matrix operator states after assembly
[cmake] pseudo code for alu flags
remove invalid assertion in rhs assembler
[cmake] enables DUNE_GRID_EXPERIMENTAL_GRID_EXTENSIONS so we can use a properly forwarding twistutil
change to local matrix proxy usage
use sionlib in df-writer/reader when available
removes copy-paste print functions