[Dune] EntityPointer finished

[Christian Engwer]

> I guess this will work after you implement a copy constructor for
> SIntersectionIterator and SBoundaryEntity.

OK... I tried this and it show you need
 SIntersectionIterator::SIntersectionIterator(const SIntersectionIterator &)
 SIntersectionIterator::operator=(const SIntersectionIterator &)
 and 
 SBoundaryEntity::SBoundaryEntity(const SBoundaryEntity &)

because SBoundaryEntity keeps a Geometry and tries to copy this.

Cheers Christian