ENH: better handling of various face types in MeshedSurface (issue #294)
- ensure that MeshedSurface and UnsortedMeshedSurface can also work with labelledTri faces. - nTriangles() convenience method for meshed surfaces - MeshedSurface::addZonesToFaces() method to copy zone information into the labelledTri per-face region storage. The goal is to replace the triSurface reading routines with run-time selectable ones from surfMesh.