Fixes #4478 - Added API localization

This PR contains 
- localization setup for apipie
- updated deps on apipie 0.2.0
- strings from apipie-rails to be included to our translation process
- all the API doc strings wrapped into N_()

Related PR in apipie-rails https://github.com/Apipie/apipie-rails/pull/232
I was not able to make it to work the way you suggest. The plan is to translate the strings in foreman and generate the i18n yaml files that will be included in apipie, so that the apipie community can benefit from our work. That worked well, but is two step process. I'll try to make it work again the way you suggested.