Teach rails the singular of Quota

This is required for reporting purposes where we actively "singularize" the name
of model objects in order to contantize and load them.

https://bugzilla.redhat.com/show_bug.cgi?id=1133132
Add Cloud Tenants and ResourceQuotas to reports

Allow users to select fields from CloudTenants and CloudResourceQuotas in
reports.

https://bugzilla.redhat.com/show_bug.cgi?id=1133132