Finalize the draft SSP model design for sections 1-13

[akarmel]

User Story:

As an OSCAL content consumer, I have a SSP model design for NIST 800.53-based SSP's in OSCAL format encompassing sections 1-13.

Goals:

- Support components for section 13
- Include support for attachments (embedded)
- Align with the component approach

Dependencies:

#257 and #267

Acceptance Criteria

1. Well documented, OSCAL draft SSP model exists for NIST 800.53-based SSP's in OSCAL format encompassing sections 1-13.

[brian-ruf]

12/20/2028. @brianrufgsa completed 100% draft of SSP metaschema. Started validation with @wendellpiez. Estimate issue is 80% complete.
Continue to work in Sprint 17.

[brian-ruf]

1/31/2019 - All of these items are reflected in the current draft of the Metaschema. Moving to review.

[brian-ruf]

2/7/2019 - still pending review for close-out.

[david-waltermire]

Closing this issue in favor of documenting new issues to define what needs to be done next.