[Dune] inconsistency with intersection methods

[Christian Engwer]

> Let is be an IntersectionIterator with is.neighbor()==true and xi a 
> point in the local coordinate system of the intersection then
> 
> is.intersectionSelfLocal.global(xi) == 
> is.intersectionNeighborLocal.global(xi) == is.intersectionGlobal.global(xi)
> 
> This condition has also been added by Mario in the theory part of the 
> Dune paper.
> 
> Question: Do we all agree on this (I do!).

I think this contition is necessary, otherwise the whole mapping is
useless. One must assume a consistent orientation of the
intersection.

Christian