Neutron Nova Interactions Support

Recent versions of Neutron are able to provide active notifications to
Nova about changes to port status and data.  This change adds the
neutron::server::notifications class to allow Puppet to configure
this feature when setting up a Neutron server.

neutron.conf requires a tenant UUID for communicating with Nova.
This changes adds adds a custom type and provider to translate an admin
tenant name to the required UUID.