Merge branch 'feature/nonlinear-gs-dynamic-localsolver' into 'master'

Add support for dynamic container of local solvers

See merge request !29
4 jobs for master in 7 minutes (queued for 9 seconds)
latest
Status Name Job ID Coverage
  Test
passed dune:git clang C++17 #177703

00:04:27

passed dune:git clang C++17 with examples #177705

00:06:58

passed dune:git gcc-8 C++17 #177704

00:06:24

passed dune:git gcc-8 C++17 with examples #177706

00:03:11