Use SQL driver for revoke backend
Add attribute to reference the RabbitMQ proposal

Should fix https://bugzilla.novell.com/show_bug.cgi?id=887112
Merge pull request #235 from vuntz/revoke-driver

Use SQL driver for revoke backend
Merge pull request #236 from vuntz/rabbitmq-attribute

Add attribute to reference the RabbitMQ proposal