Add missing translations (en); and enforce coverage.

[CloCkWeRX]

Fixes #2745

• [x] TBA - should we only run the unit tests on en locales? I can't translate to japanese easily
• [x] Alternatively, are we okay with auto translations

I took out the japanese translation, as it was 1x string.

Very annoying, I can either define the pluralisation of our models, or I can appease i18n-tasks.

• [ ] Make i18n-tasks happy with activerecord entries
• [ ] Fix specs.