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
I can never remember the rules, but is it an unspeakable sin if you go from `<h3>` to `<h1>`? I can't remember if there was some deep a11y reason that things needed to be `<h1>`-`<h6>`, in order...

http://www.w3.org/TR/html401/struct/global.html#h-7.5.5
> _Some people consider skipping heading levels to be bad practice. They accept H1 H2 H1 while they do not accept H1 H3 H1 since the heading level H2 is skipped._

But that doesn't seem to say anything official, just _some [random] people_ consider things.