Removes namespace attributes from child nodes in the pasted snippet if they are already present in the root where the snippet is pasted.

Added a test "PasteCustomControlUsingMixedTypes" that failed before this fix.
Fixed type resolve when pasting a custom control using StaticResource.
Fixed SD-1931 - Dragging Pointer from toolbox to WPF designer throws exception.
String can now be added to collections, for example a ResourceDictionary.
Support for "Bring Item To Front / Send To Back" ContextMenu ...