Merge branch 'feature/interpolation' into 'master'

.gitlab-ci.yml

dune.module

dune/multimesh/mmentity.hh

dune/multimesh/mmentityseed.hh

dune/multimesh/mmgridfactory.hh

dune/multimesh/mmgridview.hh

dune/multimesh/mmhierarchiciterator.hh

dune/multimesh/mmiteratorbase.hh

dune/multimesh/multimesh.hh

src/CMakeLists.txt

src/benchmark.cc

src/hierarchiciterator.cc

src/interpolate.cc

src/interpolation.hh

src/multigridview.cc

src/phasefield4.cc

src/profiling.cc

src/taylorhood.cc

test/CMakeLists.txt