Rewrite translation() using DjangoTranslation methods

Began with these tickets:
https://code.djangoproject.com/ticket/18192
https://code.djangoproject.com/ticket/21055

Then after opening [this pull](https://github.com/django/django/pull/1562) realized the code is too cryptic to understand any changes.

Since I already took the time to untangle how it works, refactored trans_real.translation and used DjangoTranslation to initiate new languages.