[feature][petsc] Add possibility to pass kspoptions as a string.
@andreas.dedner: This needs a bit of discussion, but it is needed, to be able to steer the PETSc solvers and preconditioners correctly.
The current approach is to pass
newton.linear.preconditioning.method: kspoptions
and then
newton.linear.kspoptions: -pc_type hypre -pc_type_hypre boomeramg
and so just like one would do when passing it on the command line.
Edited by Robert K