Add Certificate Generation and Management To Orders

Barbican can be used to automate and streamline secure generation and storage
of SSL certificates and associated private keys from client information (such
as a CSR). This feature requires being able to coordinate between multiple
possible certificate authorities (CA) for generation, Barbican for secure
certificate storage and notification once generation is completed. This
blueprint details a plugin-based approach to satisfy these requirements.

Change-Id: Ic505e3878af01c10c72544260bb38ffab610bc35