Convert all localization to use Django i18n

[13rac1]

Roundware currently isn't using the Django tools/classes/functions/methods for multi-lingual text. We should correct that.

Django docs: https://docs.djangoproject.com/en/dev/topics/i18n/translation/

Potential model translation method: https://github.com/deschler/django-modeltranslation

[IllyaMoskvin]

Related: #309, #311