TLS Data Security Overview

Here we define the overall strategy for dealing with secure TLS data
in Octavia. There are several areas that need attention, and they are
detailed in this spec. Barbican will be our default secure storage and
certificate signing service, but the interfaces should remain generic.

Sequence diagrams now included.

Change-Id: Icbbea8e37af0ce13fd959543403f2b01b8c7d17b
Implements: blueprint tls-data-security
Merge "TLS Data Security Overview"