[wip] Cloud Networking

PR for Rackspace networking. Unfortunately, it looks like none of the Rackspace operations for this service can be delegated to the Openstack Neutron code due to differences in URLs and `Network` objects.

- [x] Networks
 - [X] Operations
 - [X] Unit Tests
 - [x] Acceptance Tests
- [x] Virtual Interfaces
 - [X] Operations
 - [X] Unit Tests
 - [x] Acceptance Tests 
This is odd but here's the reasoning: Originally I thought, since there is a cloud networks endpoint, that HTTP requests for networks would be made against it. Wrong. The compute client is the one you want for all your Cloud Networking needs. And so, in the future, if the HTTP requests do actually start going to the Cloud Networks endpoint, I thought this would make it easier to change (read: backwards compatibility). Now, this raises an interesting question as to whether this should go under `compute` (or `servers`) since they share the same client/endpoint. But there does exist a `networking` service in Openstack (though Rackspace Networking has little in common with it at the moment). I'm indifferent on where it resides. When I wrote most of this service, I didn't yet know that the endpoint was not the Cloud Networks one.