Restore dock widget from settings, fixed frameless widget restore

https://discordapp.com/channels/539048679160676382/539486309882789888/593835010566521033

src/blackgui/dockwidget.h

@@ -108,6 +108,9 @@ namespace BlackGui
         //! Toggle frameless mode
         void toggleFrameless();
 
+        //! Toggle frameless deferred
+        void toggleFramelessDeferred(int delayMs = 1000);
+
         //! Window always on top
         void windowAlwaysOnTop();