Using Swift as project-based backing store for trusted services (such as Glance, Cinder)

This would allow trusted services to store data associated with a project/tenant in a separate account than the normal user's account. For example, where a user's account path is /v1/AUTH_1234, Glance could store images in /v1/IMAGE_1234. This means that while the data is owned by the project/tenant 1234, it can only be accessed via the trusted service. To access, you need two tokens: a user token (for project 1234) and a service token (for the trusted service).