(Bug 57618) Bug fix in dom-fragment unpacking of transcluded extensions

* When extensions were transcluded at the top-level, DOMFragment
  unpacking code would simply use the mw:Transclusion typeof and
  ignore the typeof on the expansion html. This lost the references
  typeof (mw:Extension/references) on the <ol> node which in turn
  meant that references were not being populated there.

* This patch fixes the unpacking to not exit dom fragment unpacking
  early and fixes the data-mw of the extension wrapper to use the
  transclusion data-mw so we get best of both worlds.

* Updated existing useless references test with useful content which
  would have caught this bug quite early on.

Change-Id: I7c4738391ca73115d8ebe23ed7a9b2587f6e22d1
Merge "(Bug 57618) Bug fix in dom-fragment unpacking of transcluded extensions"