In 1d faces and nodes have the same codimension. We assume that
the unstructured grid has a one to one mapping between the faces
and the nodes

This commit contains two bugfixes:
- The geometry type was only set to codim 0 and 1.
- To make the PolyhedralGrid work for lower dimensional grids embedded
in a higher dimensional domain (e.g., 2d grid in 3d domain), the
UnstructuredGrid dimension must equal the domain dimension. Then
all coordinates are expressed in global coordinates.

Test embedded grids in higher dimensional domains