Color & TimeSpan Editor in PropertyGrid
uses Controls from Extended WPF Toolkit fork (https://github.com/jogibear9988/WpfExToolkit)
A few small fixes for the XamlDesigner Sample App:

- fix the AvalonDock default Settings so no exception is raised
- Allow the Designed WPF View to be Tested or Rendered to a Bitmap
- Better Assembly Resolving
WPF Toolkit DLL missed for Color & TimeSpan Editor
Select Items below the current by Pressing Alt Key when Clicking on Control!