Custom content list marshaller/unmarshaller to DOM representation. This
allows you to mix data binding and document model representations for XML
within the same application. You simply use this marshaller/unmarshaller with
a linked object type of org.w3c.dom.DocumentFragment (the actual
runtime type - the declared type is ignored and can be anything). When
unmarshalling it will create a fragment to hold any content up to the close
tag for the enclosing element in the list. When marshalling, it will simply
write out any content directly.