Add the ability to use Phrase App

https://code.google.com/p/otwarchive/issues/detail?id=4015

Phrase App is a translation application that we want to use on the i18n site to allow the translation group to generate translations for the archive.

There should be no change on the test site and beta.  However check the footers still work :)

Elz has commented upon this in the past

This also fixes an issue where the headers go though the translation system twice.
Maybe ideally we should be configuring via env (I don't know that I agree with that as I feel this article isn't totally relevant to the kind of config we're doing), but moving this one single thing to env for that reason is IMO definitely not a good idea. If we overhauled config entirely then fine, but that's not what is happening here, and that would require some plan for how to manage the config in env.