LP#1638299: add release notes

LP#1638299: add release notes

Also, here is a basic testing plan:

- Upon applying the patch, verify that browse in the public
  catalog uses See, broader or narrower term, and see also
  as labels.
- Verify that scope notes now only display under the main
  heading in the browse list.
- Verify that turning off the Display related headings (see-also) in browse
  global flag disables display of see-also (related headings)
  in the public headings browse. Note that it may be necessary to
  clear memcached caching of cgf.
- Verify that see references are consistently shown.
- Verify that Server Administration | Authority Headings Fields works
- Verify that Server Administration | Thesauri now includes fields for
  short code and URI.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>