Xwt.Html5: DesktopBackend
StyleSheets: dont use Deskttop Scalefactor
Moved ImageExporter from XwtBackend to View.Visualizers
DragDrop: replaced Limaki.TransferDataInfo with Xwt.ITransferData
implement DragImage
whitespace
Xwt.Gtk: DragDrop: return all DragTypes to DragCheckEventArgs so the Target can filter it by itself - dont check it against already registered types
Xwt.Wpf: DragDrop: return all DragTypes so the Target can filter it by itself - dont check it against already registered types

TODO: use this only in DragCheck
Xwt.ITransferData: give access to DataTypes
Xwt.TransferDataStore: add DataRequestDelegate
Xwt.DragOperation: allow Image to be null
Limaki.View.DragDropAction: handle DragLeave-calles before DragDrop
Limaki.View.DragDropBackendHandler: use Xwt.Widget.CreateDragOperation instead of Widget.DragStart(data);
Limaki.View.DisplayBackend: use EventHandlers instead of overides; otherwise Xwt.Gtk.WidgetBackends dont handle DragDrops
Limaki.View.Display: use EnsureBackendLoaded
Xwt.Samples.DragDrop: use canvas with scrollview as DragDropSource