Merge branch 'cleanup/handbook' into 'master'

Cleanup/handbook3.3

See merge request !2315

(cherry picked from commit 147c17f4)

da7c3d86 [doc][handbook] change references from 3.2 to 3.3, replace broken links and update dune versions
09d74723 Merge branch 'master' of...
060d8e9f [doc][handbook] replaced the dumux version 3.3 occurances with a DumuxVersion command.
4b30139e [doc][handbook] removed some comments.