Expose Entities and Translations in API

[bugzilla-to-github]

This issue was created automatically by a script.

Bug 1409724

Bug Reporter: @stasm CC: @mathjazz Depends on: Bug 1409723 Blocker for: Bug 1409704 See also: https://bugzilla.mozilla.org/show_bug.cgi?id=1179954

• List all Entities for a Resource.
• List all Translations into a given Locale for an Entity.
  • Include status: approved, suggested, fuzzy.
  • Allow filtering on status via params?
  • ~List all Translations for an Entity~ [DONE]

Once we expose Resources, the next step is to expose Entities and their Translations. Translations have different statuses which are currently stored as boolean fields. I'd like to add as little extra logic to the API layer as possible, but perhaps it would make sense to compile those boolean fields into a single multivalued one.