Add quota support to Openstack Tenants

Adds support for collecting and storing openstack quota details form various openstack services.

Backend updates:
* Adds `cloud_resource_quotas` table and models
    * with STI to support OpenStack specific quotas
* Updates Openstack inventory collection
    * fixes the way that openstack tenants were collected
    * collects quotas based on services and tenants
        - e.g., in Tenant "ABC", the "compute" service allows for 30 vCPUs

UI Updates:
* Tenant tab in Cloud subnav
* Cloud Tenants in Openstack provider relationships lists (listnav and textual summary)
* Security Groups, Instances, and Images relationships for Tenant summary page
* Quota on Tenant summary page

NB:  Rebased this PR to remove the references to the Tenant Auth support.  I've got that stashed away as a separate branch for now.  If it turns out we still need that concept, we can go back to it.  For more information, see @roliveri's comments on outdated diffs below.

@Fryguy, @roliveri, @dclarizio, @h-kataria please review
We seem to have a non-standard way of building routes.  I could not figure out how to use our path helpers to generate the correct paths for these hardcoded URLs.  And, unfortunately, since all of the other controllers that build breadcrumbs use the same hardcoded method, I don't have a decent example to go from.

I'm going to leave this as is. Perhaps when we make the jump to rails 4, we'll clean up our routes a little...