Refactored cloud and list facets into enumerated facet

Migrated substantial amounts of common code to the EnumeratedFacet superclass.  Besides code shifting, migrated a lot of parameter gathering out of code and into relevant settingSpecs.  Introduced explicit upcalls to overridden superclass methods to permit shared code to reside in the superclasses; someday it would be nice to formalize these "before" and "after" methods using the metaobject protocol.