Merge branch 'import-examples' into 'master'

Merge the dune-tnnmg-examples module into dune-tnnmg

See merge request !18
4 jobs for master in 15 minutes and 16 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Test
passed dune:git clang C++17 #115566

00:04:50

passed dune:git clang C++17 with examples #115568

00:08:12

passed dune:git gcc-8 C++17 #115567

00:07:24

passed dune:git gcc-8 C++17 with examples #115569

00:10:25