WIP: L10n string export and import

- [x] Export strings from mustache files
- [x] Export strings from js files
- [x] Export strings from go templates
- [x] Import po files from external repo
- [x] Copy and convert po files into json
- [x] Move FindMyDevice-l10n to mozilla-services and update reference
Will our find.firefox.com/ site have an "/en-US/" folder at a root level, or do these need to be prefixed with `mozilla.{com,org}`?

Also, embedding un-translateables like "/en-US/" is going to give you a bag of hurt once we do start supporting other languages, no? Or at least force all the German and other locales into an English flow.