webhooks: initial release

* Adds REST API endpoint for receiving webhooks notifications
  from external services and pass the request payload to a
  Celery task for background processing.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
restful: apikey and oauth2 authentication support

* Adds support for API authentication via both API keys
  and OAuth 2.0.

* Adds pending deprecation messages to API authentication, which
  will be replaced by OAuth 2.0 personal tokens authentication.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
celery: eager task execution fix

* Fixes eager task execution of Celery tasks, caused by an uninitialized
  variable.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
celery: double app creation fix

* Fixes an issue where multiple Flask applications where
  created.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
accounts: blueprint move

* Moves blueprint to separate package.
accounts: blueprint move file fix

* Fixes blueprint after file move.
oauth2server: more stuff
accounts: WIP settings