Create associations between projects and endpoints

OS-EP-FILTER Implementation

There are new methods to create endpoint and project associations.
A full CRUD API to assign projects to endpoints as well as
the ability to check all the projects associated with a given
endpoint.

The association is used to pick what endpoints are visible
for the given project and a filtered catalog is built
accordingly.

During a project-scoped token request, if project-endpoint
associations have been created, the returned catalog will only
list the project linked endpoints.

blueprint endpoint-filtering

Change-Id: Idaa7f448a67e3bae01ba12686be37ba058183cf6