1) the dgf base class was not passing the communicator on to the grid factory
2) due to a default parameter the protected constructor was used when passing a
   communicator to the factory - removed default parameter seems to not cause any
   problem

length.

Problem is that with surface grids two elements can have the same barycenter and
would have only been added once into the map leading to missing elements in the grid
construction. Using a multimap is probably not the best solution since elements with the
same barycenter would be sorted to lie directly next to each other but probably they are
on opposite sides of the surface. Since will not lead to a good partitioning...

now the if clause to get the twist and not whether the item is the same

an implementation for a levelintersectioniterator for conforming refinement, that is restricted to the macro level

Because the CommDataHandleIF exports the DataType, it is indeed possible
to check whether a type T is derived from
(*)    CommDataHandle< T, typenanme T::DataType >.
We use this information to disable the generic method loadBalance( LBWeights )
in this case.

Note: If someone passes a type U derived from a type T derived from (*),
there is no way of checking this. In this case, the wrong method will be
used, hopefully resulting in a compile time error.

Note: As a side effect, the iterator test triggers an error in the edge
iterator of a 2d grid. Here, not all entities are visited.

grids seems not to work.