implement ProxySongList for handling general operations on lists

src/search_engine.h

@@ -96,12 +96,10 @@ class SearchEngine : public Screen< NC::Menu<SEItem> >, public Filterable, publi
 		virtual void prevFound(bool wrap);
 		
 		/// HasSongs implementation
-		virtual MPD::Song *getSong(size_t pos);
-		virtual MPD::Song *currentSong();
+		virtual std::shared_ptr<ProxySongList> getProxySongList();
 		
 		virtual bool allowsSelection();
 		virtual void reverseSelection();
-		virtual void removeSelection();
 		virtual MPD::SongList getSelectedSongs();
 		
 		virtual NC::List *GetList() { return w->Size() >= StaticOptions ? w : 0; }