Merge branch 'python3' into 'master'

See merge request [!420]

  [!420]: Nonecore/dune-grid/merge_requests/420

Merge branch 'feature/require-cmake-3.13' into 'master'

See merge request [!419]

  [!419]: Nonecore/dune-grid/merge_requests/419

Merge branch 'fix/remove-unused-cls-capture' into 'master'

See merge request [!416]

  [!416]: Nonecore/dune-grid/merge_requests/416

Merge branch 'rename-recipe-main-page' into 'master'

ref:core/dune-grid\> Rename recipe main page for consistency with PDELab
recipes. (The old name caused name clashes when building the website; the new
naming scheme should allow recipes for all dune modules)

See merge request [!418]

  [!418]: gitlab.dune-project.org/core/dune-grid/merge_requests/418

Rename recipe main page for consistency with PDELab recipes. (The old name caused name clashes when building the website; the new naming scheme should allow recipes for all dune modules)

Merge branch 'recipes' into 'master'

ref:core/dune-grid\> Add recipes to dune-grid

See merge request [!375]

  [!375]: gitlab.dune-project.org/core/dune-grid/merge_requests/375

Merge branch 'remove-ug-format-creation-part2' into 'master'

ref:core/dune-grid\> It is not used anymore.

See merge request [!413]

  [!413]: gitlab.dune-project.org/core/dune-grid/merge_requests/413

It is not used anymore.

Merge branch 'remove-ug-format-creation' into 'master'

ref:core/dune-grid\> The old UG3 formats are on their way out, and the call is
not necessary anymore.

See merge request [!412]

  [!412]: gitlab.dune-project.org/core/dune-grid/merge_requests/412

The old UG3 formats are on their way out, and the call
is not necessary anymore.

Merge branch 'bugfix/py/speedupIndexSetMethod' into 'master'

See merge request [!411]

  [!411]: Nonecore/dune-grid/merge_requests/411

Merge branch 'feature/communication-future-obj' into 'master'

ref:core/dune-grid\> This MR provides suggestions how to enable a future
object for non-blocking communication. If the grid implementation does not
provided this then a dummy object is returned that will print a warning if the
features are to be used.

The call

    gridView.communicate( ... ) 

will work in any case. However, code that now uses

    auto future = gridView.communicate( ... ) 

will fail if there is not at least a dummy future returned. This MR fixes this
issue in the interface class, in case the implementation still returns void.

See merge request [!311]

  [!311]: gitlab.dune-project.org/core/dune-grid/merge_requests/311

Merge branch 'bugfix/fix-factory-geogrid-constructor' into 'master'

ref:core/dune-grid\> We need to use shared_ptr for hostGrid and coordinates
like in the other constructors.

See merge request [!407]

  [!407]: gitlab.dune-project.org/core/dune-grid/merge_requests/407

We need to use shared_ptr for hostGrid and coordinates like in the
other constructors.

dune-common.

object. If the grid implementation does not provided this then a dummy
object is returned that will print a warning if the features are to be
used.

Merge branch 'feature/replace-hybrid-ifelse' into 'master'

See merge request [!404]

  [!404]: Nonecore/dune-grid/merge_requests/404

Merge branch 'bugfix/MissingAppend' into 'master'

See merge request [!403]

  [!403]: Nonecore/dune-grid/merge_requests/403

Merge branch 'feature/addPythonBindings' into 'master'

See merge request [!402]

  [!402]: Nonecore/dune-grid/merge_requests/402

grid manager then yaspgrid

# Conflicts:
#   CHANGELOG.md

The subIndex methods of the two UGGridIndexSet implementations
contains a lot of compile-time case switching.  This was
previously implemented using Hybrid::ifElse, which worked,
but it wasn't the pinnacle of beauty.  This patch reimplements
the method using 'if constexpr' instead, which has been allowed
post dune-2.7.

loadBalance with targetProcessors and handler for element data

remove python 2 support code
use utility instead of compatibility

Python bindings, default is OFF.

[feature][CI] enable Python bindings.

move imports in testpython script so that no failure happpens in case that
python packages not found
corrected PYTHON_PATH in .gitlab-ci.yml
reduce length of pythontest