Merge branch 'releases/2.6' into 'cherry-pick-9d77c363'

CHANGELOG.md

CMakeLists.txt

LICENSE.md

dune/grid/albertagrid/capabilities.hh

dune/grid/albertagrid/gridview.hh

dune/grid/albertagrid/intersection.cc

dune/grid/albertagrid/intersection.hh

dune/grid/common/capabilities.hh

dune/grid/common/grid.hh

dune/grid/geometrygrid/capabilities.hh

dune/grid/geometrygrid/grid.hh

dune/grid/geometrygrid/gridview.hh

dune/grid/geometrygrid/indexsets.hh

dune/grid/identitygrid.hh

dune/grid/io/file/vtk/vtkwriter.hh

dune/grid/onedgrid.hh

dune/grid/test/staticcheck.hh

dune/grid/test/test-geogrid.cc

dune/grid/test/yasp/CMakeLists.txt

dune/grid/test/yasp/test-yaspgrid-entityshifttable.cc