Sprout - appliance spring

Django/celery based appliance spring caretaker.

* Configure templates
* Deploy appliances on-demand
* Keep a pool of spinned appliances
* Spread the appliances across providers

More informations in the MOJO document I posted recently.
This class and the mapping below might be handy in `utils.mgmt_system`, I think it's be great to eventually have the vm_status methods on those classes return these Power constants rather than the strings they're returning now.