[wip] Glance service

Preliminary support for the [Glance v2 image API](http://docs.openstack.org/api/openstack-image-service/2.0/content/). All of the [JSON schema stuff](http://docs.openstack.org/api/openstack-image-service/2.0/content/get-image-schema.html) will make this... interesting :thought_balloon: 

This is my first attempt at integrating with the new architecture, so please give me a heads-up if you see me using anything incorrectly.