Coboundary range construction from elements

[karlrupp]

Right now one has to write

for (VertexIterator vit = ...)
{
   EdgeOnVertexContainer edges_on_vertex(domain, vit.handle());
   ....
}

I find it non-intuitive to call .handle() on the iterator. Instead,

for (VertexIterator vit = ...)
{
   EdgeOnVertexContainer edges_on_vertex(domain, *vit);
   ....
}

should also work, which is not the case at the moment.

[karlrupp]

Problems stems from assignment troubles in coboundary_range_wrapper and thus invalidates the correct dereference_handle() to be called

[FlorianRudolf]

done in 3f7c8f3