Feature/istl solver factory

Closes #810 and #652

See merge request !1845

[tests][2pncminni] rename forgotten fvGridGeometry occurences to gridGeometry

See merge request !1880

[cleanup] Remove old unused simulation steering functions in problem

See merge request !1878

Backwards-compatible implementation. Legacy parameter names
e.g. PreconditionerIterations will still work but subgroup params
overwrite them, e.g. Preconditioner.Iterations.

Markus Blatt authored 5 years ago and Timo Koch committed 5 years ago

This requires a version newer than 2.7.0. The backend translates
the configuration parameters from Dumux CamelCase to the dune-istl
names. If a Dumux parameter is not found we fall back to using
the dune-istl parameter name.

We fall back to the parallel AMG backend if the DUNE version is
not sufficient.

Feature/remove amg deprecation warnings

See merge request !1869