Merge branch 'feature/addPythonBindings' into 'master'

See merge request [!363]

  [!363]: Nonedune-fem/dune-fem/merge_requests/363

Python bindings, default is OFF.

Merge branch 'bugfix/fixrefelementcall' into 'master'

See merge request [!362]

  [!362]: Nonedune-fem/dune-fem/merge_requests/362

Merge branch 'feature/freeStandingLocalFunction' into 'master'

See merge request [!361]

  [!361]: Nonedune-fem/dune-fem/merge_requests/361

Merge branch 'feature/removedDep2.7' into 'master'

See merge request [!360]

  [!360]: Nonedune-fem/dune-fem/merge_requests/360

fix some runner issue

fix

reduce a single image test

test

use std=c++17

remove debain 9 and try ubuntu 18 with clang

fix

removed deprecate method after 2.7 released

Merge branch 'revert-2a553cf0' into 'master'

ref:dune-fem/dune-fem\> This reverts merge request [!357]

See merge request [!358]

  [!357]: gitlab.dune-project.org/NoneNone/merge_requests/357
  [!358]: gitlab.dune-project.org/dune-fem/dune-fem/merge_requests/358

This reverts merge request !357

Merge branch 'feature/removeDep2.7' into 'master'

See merge request [!357]

  [!357]: Nonedune-fem/dune-fem/merge_requests/357

Merge branch 'patch/remove-alt-istlinverseoperator' into 'master'

ref:dune-fem/dune-fem\> removes solver/istl.hh. the file was disabled since it
is missing several included files and clashes with solver/amgistl.hh

See merge request [!346]

  [!346]: gitlab.dune-project.org/dune-fem/dune-fem/merge_requests/346

Merge branch 'feature/hierachical' into 'master'

ref:dune-fem/dune-fem\> also needs to be backported to 2.7

See merge request [!349]

  [!349]: gitlab.dune-project.org/dune-fem/dune-fem/merge_requests/349

Merge branch 'bugfix/cleanup-utility' into 'master'

See merge request [!354]

  [!354]: Nonedune-fem/dune-fem/merge_requests/354

Merge branch 'bugfix/missingapplyinverse' into 'master'

See merge request [!353]

  [!353]: Nonedune-fem/dune-fem/merge_requests/353