WIP: L10n string export and import

- [x] Export strings from mustache files
- [x] Export strings from js files
- [ ] Export strings from go templates
- [x] Import po files from external repo
- [x] Copy and convert po files into json
- [ ] Move FindMyDevice-l10n to mozilla-services and update reference
Yep I agree that it should. I'll take a look. The content server is doing it this way, and I forgot to change it. Thanks for noticing :smile:.