User story:
As a VE user,
WHEN I use there's already a named reference with main content
AND I use the sub-menu in the reuse dialog to add a sub-reference for that reference
THEN I can create a new sub-reference that's referring the main content of the former
Acceptance criteria:
GIVEN
<ref name="book">Miller</ref>
WHEN I add a sub-ref reusing book with the content page 1
AND I save the changes in VE
THEN a new sub-ref with the same name is added
<ref name="book">Miller</ref> <ref name="book" details="page 1" />