Make some changes to clarify when the code is using the internal
project ID or the external project ID.
The SQL command ForeignKey marks a requirement that two tables are kept
in sync with a common key. We want to ensure that for every project
quota record, there is a matching project record in the projects
table.
Also add the migration script that adds the project quotas table
to databases based on an older Barbican database model.
Change-Id: I860c87182d94967a290534e2825404f2df2e4033
Implements: blueprint quota-support-on-barbican-resources
652f101c45