refs #419, reviewed style sheet paintEvent code

* removed for QWidget
* added for QDialog
http://stackoverflow.com/questions/37952348/enable-own-widget-for-stylesheet

src/blackgui/overlaymessagesframe.h

@@ -81,9 +81,6 @@ namespace BlackGui
         void showOverlayImage(const BlackMisc::CPixmap &pixmap, int timeOutMs = -1);
 
     protected:
-        //! \copydoc QFrame::paintEvent
-        virtual void paintEvent(QPaintEvent *event) override;
-
         //! \copydoc QFrame::keyPressEvent
         virtual void keyPressEvent(QKeyEvent *event) override;