CatalogSearcher is not an extension of MetaSearcher

[Fxp]

LuceneSearcher, UnusedSearcher and Z3950Searcher are all extensions of MetaSearcher but CatalogSearcher for CSW is not. This is ok until CatalogSearcher is put into the session as Geonet.Session.SEARCH_RESULT where up until now only the extensions of MetaSearcher were expected. Because CatalogSearcher is not a MetaSearcher the nice polymorphism/dynamic binding used for example when closing the searcher (get a MetaSearcher and do searcher.close()) is broken and we need to do ugly if (object instanceof LuceneSearcher) then .... else etc etc etc. Action: make CatalogSearcher an extension of MetaSearcher or put it somewhere else in the session.