Fix MeshQuality to work with CellSetSingleType
MeshQuality filter only worked with
MeshQuality should also work with
MeshQuality to work with both.
The handling of cell sets was actually worse than that. After forcing
the type to
CellSetExplicit<>, it then applied a policy that converted
the types back to all possible cell sets. Thus, the filter made lots of
code paths that were impossible to follow.