Add RabbitMQ permissions for the email alert service.

The obnoxiously long names are a side effect of
needing them to be unique both across apps and
functionally within an app to avoid concurrency
clashes.

We're looking at ways to mitigate this and improve
test/prod parity.
Merge pull request #214 from alphagov/add-email-alert-service-rabbitmq-perms

Add RabbitMQ permissions for the email alert service.