Ref T225, force stylesheet in CForm base class and used by all forms

* Allows to use stylesheet attributes like [readonly]
* changing to "readonly" applies correct stylesheet

src/blackgui/editors/form.h

@@ -59,6 +59,9 @@ namespace BlackGui
             //! Pasted from clipboard
             void pasted();
 
+            //! \copydoc BlackGui::CGuiUtility::forceStyleSheetUpdate
+            void forceStyleSheetUpdate();
+
             bool m_readOnly = false; //!< read only
         };