* The deprecated interface exists and should be marked override
  at least until release 2.8 including the release.
* After 2.8, i.e. 2.9-git the interface can be removed and is
  also removed here in foamgrid

Simon Praetorius authored 5 years ago and Timo Koch committed 5 years ago

Due to upstream changes in dune-common. Backward-compatible with pre dune 2.7.

Constructing a geometry to get the type is always more expensive if
you just need the type. This implement the more efficient interface.

Instead of storing a nullptr and document undefined behaviour we
can actually store a this pointer and have perfectly defined behaviour.