_refs should include _tagRefs as well

(User Story, Closed -> Fixed, Priority: Critical, Test Status: Unit tested , Reported By Justin du Coeur, )
Summary: This is long since overdue -- the _refs / _tagRefs distinction is a fiddly detail that doesn't make any sense from an end-user POV.
Depends Upon:
As a first pass, it's probably acceptable for this to only be the case for the broad case that doesn't filter by property -- that might make this easier to implement.
This is critical path for automatically showing refs on a Thing's Default View.
Note that _refs currently requires a Property, which _tagRefs doesn't. To fix this, we need to start by enhancing _refs.