ENH: support different iso-algorithms (#1374)
- add an 'isoAlgorithm' keyword to distance surface and cutting plane to advance further testing of the isoSurfaceTopo algorithm. Does not yet handle the full spectrum of bound boxes, cellZones etc.
- add an 'isoAlgorithm' keyword to distance surface and cutting plane to advance further testing of the isoSurfaceTopo algorithm. Does not yet handle the full spectrum of bound boxes, cellZones etc.