Merge branch 'fix/dune-version-requirements-solverfactory' into 'master'
[istl] Parallel solver factory only available from Dune 2.8 onwards
Closes #980 (closed)
See merge request !2437 (merged)
(cherry picked from commit 7f01e586)
b1160723 [istl] Parallel solver factory only available from Dune 2.8 onwards