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.
I have some style comments. It's not technically wrong, but we try to keep some stylistic consistency, and leaving a space before the next item in an iteration is one of them. Also, Ariana has us switching to the "single quote around strings unless they need interpolation" style in Ruby. (So the whole thing would be: ```ts('Footer', key: 'footer')```).