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/aircrafticaoform.cpp

@@ -190,6 +190,8 @@ namespace BlackGui
             ui->cb_Rank->setEnabled(!readOnly);
             ui->drop_DropData->setVisible(!readOnly);
             ui->combined_TypeSelector->setReadOnly(readOnly);
+
+            this->forceStyleSheetUpdate();
         }
 
         void CAircraftIcaoForm::setSelectOnly()