Move RSS settings to a separate dialog

src/GUI.h

@@ -166,6 +166,7 @@ private:
   QPointer<RSSImp> rssWidget;
 
 private slots:
+    void on_actionRSS_Reader_triggered();
     void on_actionSpeed_in_title_bar_triggered();
     void on_actionTop_tool_bar_triggered();
 };