Comment 4 for bug 1790231

I've pushed two additional commits to working branch user/jeffdavis/lp1790231-subject-heading-link-exact-match-search. The first new commit accommodates genre and other facet-based subjects where we don't want exact match. The second new commmit applies the fix when display fields are not in use, e.g. when you access the record directly without search terms. All three commits should probably be squashed before merging to master.