Migrate All Certification Artifacts to RESO Transport Specifications

[darnjo]

In order to unify the generated artifacts so that all programs can use them, we will move them out of this repository and place them in the RESO Transport Specifications repo, aka RTS.

This will involve a bit of work, including the following:

• Move reference DD sheets to RTS, then add as submodule.
• Create process to generate BDD test artifacts to RTS on successful build and PR against RTS.
• Generate version-specific reference OData XML Metadata and PR to RTS.
• Publish Open API spec documents from reference metadata and PR to RTS as well as publish to SwaggerHub.
• Generate reference metadata report used for RESO Certification and PR to RTS.
• Add hooks to RTS submodule for Certification acceptance testing.
• Update all relevant documentation.
• Update relevant external links.