Merge branch 'feature/use-adl-for-range-based-for-loops' into 'master'

[range-based-for] Use ADL as intended by dune

Argument dependent lookup deduces the Dune namespace from
the function arguments that are also in namespace Dune.

see https://www.dune-project.org/doc/doxygen/html/group__GIIteration.html

See merge request !65