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
Or, if you want to go completely off the rails, we could use [font-awesome social media icons](http://fortawesome.github.io/Font-Awesome/icons/#brand) and then nothing would need translations (at the expense of consistency or whatever).

http://fortawesome.github.io/Font-Awesome/icon/twitter/
http://fortawesome.github.io/Font-Awesome/icon/twitter-square
http://fortawesome.github.io/Font-Awesome/icon/facebook
http://fortawesome.github.io/Font-Awesome/icon/facebook-square/
http://fortawesome.github.io/Font-Awesome/icon/youtube