that case is simply not implemented.

consecutive boundarySegmentIndex.

- reverts previous implementation of boundarySegmentIndex to the old
segmentId
- introduce a boundary segment index set that provides a consecutive
index set for macro boundary segements.

GenericGeometry backport.

With this patch, Entity::father, Entity::subEntity,
IntersectionIteratorWrapper::inside and IntersectionIteratorWrapper::outside
return entities instead of entity pointers.

Warning: This will definitely break compatibility with the 2.3 release.

It is deprecated in Dune 3.0

- macroId(element) returning a globally unique consecutive integer id
- master(element)  returning the master process for the given entity
- weight(intersection) returning (an upper bound) for the communication cost for this intersection
With these three methods a dune sided call to a graph partitioner (e.g. Zolan) becomes possible.
The three methods can also be moved to the Entitiy/Intersection class but this approach a better capsulation of
the new features. The weight method does not take anything like filtering, possible communication on
not leaf level into account, or varying sizes for the communicated data into account...