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
*documenting