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/dockwidgetinfobar.cpp

@@ -7,6 +7,7 @@
  * contained in the LICENSE file.
  */
 
+#include "guiutility.h"
 #include "dockwidgetinfobar.h"
 #include "components/maininfoareacomponent.h"
 #include "stylesheetutility.h"
@@ -21,6 +22,7 @@ namespace BlackGui
 {
     CDockWidgetInfoBar::CDockWidgetInfoBar(QWidget *parent) : CDockWidget(parent)
     {
+        this->setProperty("mainframeless", CGuiUtility::isMainWindowFrameless());
         this->setMarginsWhenDocked(0, 0, 0, -1);
         this->setWindowTitle("Info bar");
         this->setWindowIcon(CIcons::swift24());