[ordering] add paranoiy checkt to ensure that the geometrytype is compatible with what we precomputed

Some FEM implementations use hard-coded GeometryTypes, this can lead to the ugly siutation,
that we precompute certain offsets for these GeometryTypes, but the grid acutally yields other
types. In this situation the container indices are wrong. This additoinal check makes sure that
we con't accidentially run into this problem. On the long run we should fix the FEM implementations
[test] update testordering to trigger a bug, I've been hunting for several days

VariableMonomFEM on triangular meshes lead to ``unexpected'' results. One could also say
it totally fails. This worked for older versions of PDELab, but since PDELab got a clever FEM and
can reduce the memory footprint to compute DOF indices, we run in problems, when the
GeometryType doesn't fit to that of the mesh.
[Bugfix][VariableMonomFEM] allow to set the GeometryType in the constructor

a not so nice workaround for the BUG triggered in the last patch