We need to compute quite a few global reductions in the
Newton method of opm-autodiff. This commit adds the functionality
to compute several reductions combined using only one global
communication. Compiles and test succeeds with one or more process.
To support this the solveSystem methods of the LinearSolverInterface gets
an optional additional template parameter of type boost::any. It can hold any
copy constructable object. In our case it is used to pass the information about
the parallelization into the solvers of dune-istl without the compiler needing to know
their type. Inside of LinearSolverIstl::solveSystem we check whether the type stored inside of
boost::any is the new ParallelIstlInformation. If this is the case we extract the information
and use the parallel solvers if available, otherwise we solve serial/sequential.
The new ParallelIstlInformation is needed as the OwnerOverlapCopyCommunication is not copy
constructable. This is indeed a design flaw that should and will fixed upstream, but for the
time being we need ParallelIstlInformation to transfer the ParallelIndexSet and RemoteIndices
objects.
