As a user I want to be able to interact with the app in another language

[longhotsummer]

We need to mark most strings for translation. We support translation for document content, but not for the app itself.

• [ ] indigo
• [ ] indigo_api
• [ ] indigo_app
• [ ] indigo_content_api
• [ ] indigo_metrics
• [ ] indigo_resolver
• [ ] indigo_social
• [ ] indigo_za