add subject to optional allowed scopes
single module for the panoptes doorkeeper scopes
ensure public scope is included on the app scopes
Merge pull request #314 from camallen/subject_scope

add subject scope to doorkeeper
Make users bannable.

- Short-circuit non-get requests for banned users
- Close #247
Merge pull request #316 from edpaget/ban-users

Make users bannable.
scrub sql error messages from json_responses

do not expose any internal schema / access control messages in the response object.
keep terminology in the api layer consistent