some refactoring: removed ugly terminology: CachedLocally,
CachedGlobally. Must be completed by removing duplication
morph(),apply(), and by changing/integrating Result.
Indeed Result and Operation refer to the same interface! or not?
almost-removed Result and CachedResult (moved them into obsolete
package).
renamed OperationBase to AbstractOperation
renamed Operation to OperationStructure because it extends, rather
peculiarly, Structure