refs #335, style sheet fixes / improvements and support methods

style sheets:
* style sheets with background textures
* scroll area / toolbox style sheet fix
* floating dock widgets
* kept 1st version of stylesheets in backup directory
* removed maininfoarea stylesheet, no longer needed with fixed style sheet

code
* central paintEvent method to enable style sheets in derived widgets
* detect frameless windows, dynamic properties

src/blackgui/components/infowindowcomponent.h

@@ -68,6 +68,10 @@ namespace BlackGui
 
             //! Current page
             void setCurrentPage(QWidget *widget);
+
+        private slots:
+            //! Style sheet changed
+            void onStyleSheetsChanged();
         };
     }
 }