Finalize and publish p-19, p-0 as active, proper document TOC and titles

[gregelin]

Finalize p-19 with RMF tailoring statement, toc, update instructions

Add RMF tailoring statement to describe GovReady PBC security philosophy. Add table of contents. Rename 'About this document' to 'Abstract'. Add 'Motivation', 'Update and Comments', 'Auxilary Files' sections. Remove 'Practice', 'Purpose' sections. Add in

,

, and

tags. Move p-19 into main practices directory. Update p-0.

Also changed formatting of p-0 to have keys. Placed 'ts' codes to right of Practice title in listing tables for better readability.