[tutorial][ex3] Bring exercise 3 to current state. Probably dune_add_test still has to be commented in CMakeLists.txt shortly before the dumux course, as the exercise required uncommenting.
[tutorial][ex3] Bring exercise 3 to current state. Probably dune_add_test still has to be commented in CMakeLists.txt shortly before the dumux course, as the exercise required uncommenting.