Merge branch 'revert-eed0ae80' into 'master'

ref:pdelab/dune-pdelab-tutorials This reverts merge request [!68]

See merge request [!70]

  [!68]: gitlab.dune-project.org/NoneNone/merge_requests/68
  [!70]: gitlab.dune-project.org/pdelab/dune-pdelab-tutorials/merge_requests/70