MarkupExtensionWrapper is now public to make it possible to make wrappers for non-standard markup extensions. Wrapper can be registered by applying MarkupExtensionWrapperAttribute or calling the static method RegisterMarkupExtensionWrapper of the MarkupExtensionWrapper class.
Merge pull request #627 from gumme/WpfDesignerMarkupExtensionWrapper

MarkupExtensionWrapper is now public to make it possible to make wrapper...