Merge branch 'feature/vetorization-unstructured-grids-cherry-pick' into 'master'

ref:extensions/dune-codegen

-   Make it possible to do vectorization on unstructured grids
-   Move most things concerning permutations into the interface classes of the
    sumfact kernel
-   Add test cases for all variations of facedir and facemod

See merge request [extensions/dune-codegen!285]

  [extensions/dune-codegen!285]: gitlab.dune-project.org/extensions/dune-codegen/merge_requests/285