Docs: Translator acknowledgements and PostgreSQL support

Docs: Translator acknowledgements and PostgreSQL support

Updates the release notes with acknowledgements for translators that changed
trasnlations strings for offically-supported languages since the last release.
Also adds PostgreSQL as a recommendation as per discussion at March 2017 dev
meeting and follow-up e-mail to the dev list.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>