Feature: Documentation Tools

[mrshll1001]

This PR brings in a sphinx-doc build compatible with Read The Docs, as well as a Python Script designed to support quickly generating a Schema Reference page from arbitrary schema files.

Features:

• Generate tabular representations of the Profile schemas (Schema Reference page)
• Generate ERD diagram from Profile schemas (Entity Relationship Diagram page)
• Generate API reference from Profile's OpenAPI file (API Reference page)
• Guidance inside of README.md
• In-line tutorials to support more advanced usage (included in the source files for each docs page)
• Template pages to scaffold getting some comprehensive docs up quickly
• Read The Docs configuration

This responds to community need for a "Minimal Profile". When this is integrated, you can clone this repo and spin up your entire Profile and its Documentation from one place!

[mrshll1001]

Merging sans review in order to enable development of OR UK Profile docs site. We can review the inline documentation later, as this is non-normative.