Update install script to pre-3.2 release status

See merge request !86

Update coupled PMF-FF exercise to use the reordered matrix and solution vector

Closes #23

See merge request !87

[cleanup] Remove AMG deprecation warning

See merge request !82

Fix/removing some inconsistencies

See merge request !81

[cleanup] rename all local occurences of EnableFvGridGeometryCache to

See merge request !79

EnableGridGeometryCache

use new names G(g)ridGeometry

See merge request !78

Reflect the change introduced by commit 83fe871a to the Dumux master.
Prevent deprecation warnings.

Towards a more consistent DUMUX course for version 3.1

Closes #21

See merge request !77

[course][exercises][naming] adapted towards the general naming conventions, unified naming of files and executables for the course

[course][exercise][biomin] problem: corrected sign of eps_, Readme: commented on neglecting NH4 and removed wrong explicit line numbers

[course][exercises] Use new gravity method

See merge request !75

[course][exercises] Correct return type for Neumann and Source functions

See merge request !76