Fixed a broken test.
Added console output for debugging (now commented out).
A bunch of refactoring, moving some things from Mesh to MeshTopology.  Made GDA responsible for cubature degree determination, at least default cubature degree determination, and added a setter that gives MeshTopology access to the GDA, so that it can compute curvilinear elements without explicit dependence on Mesh.  (If GDA is not set, will use linear cubature for such purposes.)

Note that the MeshTransferFunction fails the CellMap test on > 1 MPI process.