- old 'DELETE' enum was easily confused with 'REMOVE', which removes
the set, not the elements from the set.
- provide corresponding subtractSet() method
STYLE: HashSet set/unset instead of insert/erase methods in topoSetSource
- simplifies switching to/from bitSet storage
- the dictionary-driven variant of stitchMesh allows sequential
application of 'stitch' operation with requiring intermediate
writing to disk.
- Without arguments:
* stitchMesh uses a system/stitchMeshDict or -dict dict
- With arguments:
* master/slave patches specified on the command-line as in previous
versions.