Return primal meshes in series

Currently, a primal geometric map series returns dual meshes, which are the dual meshes associated with the subdivisions of a provided primal mesh.

However, for the purposes of e.g. plotting, we often want to visualize results on the finest primal mesh. To access the primal mesh, you have to either perform an ACSet transformation on the finest dual mesh, or recreate the finest mesh by "manually" subdividing the coarse primal mesh that you provided.

It would be convenient to instead also return the primal meshes in the series.