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.
support migrated project subject locations

migrated projects will have subject locations as per { "standard" => "S3 public url" }.
avoid n+1 subject version queries

https://github.com/airblade/paper_trail/issues/222
extract helper class
flag migrated subjects

Add support for legacy subject existing s3 locations.
pivot on subject metadata
fix schema merge conflict