Added client registration caps to OAuth plugin

Added client registration caps to OAuth plugin

THE MIGRATIONS SUPPLIED WITH THIS COMMIT WILL DROP AND RE-CREATE YOUR
oauth__tokens AND oauth__codes TABLES. ALL YOUR OAUTH CODES AND TOKENS
WILL BE LOST.

- Fixed pylint issues in db/sql/migrations.
- Added __repr__ to the User model.
- Added _disable_cors option to json_response.
- Added crude error handling to the api.tools.api_auth decorator
- Updated the OAuth README.
- Added client registration, client overview, connection overview,
  client authorization views and templates.
- Added error handling to the OAuthAuth Auth object.
- Added AuthorizationForm, ClientRegistrationForm in oauth/forms.
- Added migrations for OAuth, added client registration migration.
- Added OAuthClient, OAuthUserClient models.
- Added oauth/tools with require_client_auth decorator method.