Ref T573, allow different color in XPDR mode component from stylesheet

* changed signal to trigger reload of stylesheet (only way to update dynamic properties)
* made infobar left aligned (and not spacer aligned), better scaling
* adjusted qss

src/blackgui/components/transpondermodecomponent.h

@@ -36,6 +36,10 @@ namespace BlackGui
             //! Dtor
             virtual ~CTransponderModeComponent() override;
 
+        signals:
+            //! value has been changed
+            void changed();
+
         private:
             QScopedPointer<Ui::CTransponderModeComponent> ui;
             BlackMisc::Aviation::CTransponder m_transponder;