Added networking to the Deployment and Role models

FIXME: not merge-worthy yet, but I wanted to get this
work-in-progress out there before I'm offline for a couple
days.

Since 'nova' vs 'neutron' networking is a deployment-level
choice that affects the Roles (i.e. Hostgroup types) that
are activated, this commit adds metadata to the role model
to identify a role as being used for nova, or neutron, or both.
In addition, deployment now has a field to identify it as a
nova deployment or a neutron deployment.
Add additional :through association to get roles from deployments

This isn't ready to merge. It's not tested yet, and it may need
some tweaks for the association itself to work properly.
add Role/Service/Layout/Parameter data to seeds.rb

This is a work in progress, not yet ready to merge