Include XForms module in Reference Application

The 2.x reference application includes the HTML Form Entry module, via the htmlformentryui module. We should include the XForms module too.

Acceptance Criteria

1. The implementation-defined forms feature in RA-304 should let you attach XForms to the UI
2. When you click to fill out an XForm, it should open in a page framed by the 2.x UI, with a correct breadcrumb (equivalent to HFEui's enterHtmlFormWithStandardUi)
3. Entering an XForm for a visit should set the encounter's visit field correctly
4. An encounter entered via XForm should "look good" in the Visits page both in its compact view and its expanded view. (The expanded view needs to be lightweight, e.g. it shouldn't bootstrap GWT.)
5. From the Visits page, an encounter entered via XForm should be editable via the XForm that was used to create it. (The edit page should have correct breadcrumbs, as in HFEui's editHtmlFormWithStandardUi.)

(It's possible that these last two ACs can't be fulfilled without first solving RA-435. If you're submitting a fix to this ticket without solving those last two points, make sure that RA-435 mentions XForms as well as HTML Form Entry.)