Appliance util

Built on @jkrocil's work in #449, with some tweaks.

* utils.appliances became utils.appliance, despite what my crappy commit message says. I think it reads better this way, but it's literally a superficial change.
* `utils.ssh_client.SSHClient` didn't get smarter after utils.conf was invented, but should have, so I fixed that here. It can probably be further improved by using `self.address` for hostname, so `Appliance.ssh_client` behaves more predictably
* `provider_factory` was already being imported, so it seemed like a good idea to use that to get at the underlying management system object, which makes instantiating an Appliance in a python shell very easy now.
* self.version wasn't being used by anything in the class, so I pulled version out of the class init. We can get the appliance version from the appliance itself (it's in `/var/www/miq/vmdb/VERSION`); having it as an init param seemed a little fragile in the long run
* The class init time was a little onerous, so I move `self.address` into a lazily evaluated property.
* The rename method makes use of the db conf yaml mangler that I wrote in #457

@jkrocil, let me know if this works for you in #401

closes #449