WIP Editor

The editor must:

- [x] list translation per domain
- [x] select a translation
- [x] save translation
- [x] not allow saving empty translation
- [x] change source/target locales (reload translation list + selected translation)
- [x] change domain (reload translation list + keep selected translation?)
- [x] select first translation on page load (on domain change ?)
- [x] approve/unapprove a translation

Later:

- select next item 
- keyboard navigation
- filter translation list