Closed requested to merge edscott.wilson/dumux:install-fix into releases/3.1
**This MR fixes the "make install" instruction / DuMux needs it so user can do a standard make install without having to hack source **:
**Which issue this MR fixes: Fixes install references to non existing files.
Special notes for your reviewer:
I think I have the merge request done correctly by updating my local fork to the current releases/3.1 branch.