Allow to make truncation gradient aware

This additionally checks if the gradient points
inside of the admissble set for those entries
touching the obstacle.
4 jobs for feature/gradient-aware-truncation in 14 minutes and 20 seconds (queued for 5 seconds)
Status Name Job ID Coverage
  Test
passed dune:git clang C++17 #169775

00:04:31

passed dune:git clang C++17 with examples #169777

00:07:40

passed dune:git gcc-8 C++17 #169776

00:06:58

passed dune:git gcc-8 C++17 with examples #169778

00:09:49