Add nova manage and client wrapper libraries

- Add nova-manage and novaclient wrapper libraries for interacting with
  those resources. The nova-manage wrapper supports things like ssh
  access in the event that nova-manage is not on the same machine as
  poncho.

- Move cmd/service-worker.py -> cmd/service_worker.py.

- Fix minor bugs in cmd/service.py and workflows.py.

- Add cmd/service_worker.py to setup.py as another command.