Rate limiting for Quantum API

The goal of this blueprint is to implement rate limits for the Quantum API in a way similar to what has been done for the Openstack API.

From the Openstack API developer guide:
"Rate limits are specified in terms of both a human-readable wild-card URI and a machine-processable regular expression. The human-readable limit is intended for displaying in graphical user interfaces. The machine-processable form is intended to be used directly by client applications."

Rate Limiting will be implemented as a separate module in the Quantum pipeline. We will explore whether work in the Openstack-commons project can be reused (or alternatively volunteer for rate limiting in Openstack-commons and use it in Quantum)