add ScreenType for screen's type identification

src/server_info.h

@@ -33,6 +33,7 @@ struct ServerInfo: Screen<NC::Scrollpad>, Tabbable
 	virtual void resize() OVERRIDE;
 	
 	virtual std::wstring title() OVERRIDE;
+	virtual ScreenType type() OVERRIDE { return ScreenType::ServerInfo; }
 	
 	virtual void update() OVERRIDE;