Clarify that open registration is required.  Closes #19.
Clarify that JWT introspection is recommended, not required for now. Closes #21.
Clarify the matching algorithm for fixed registration parameters. Closes #22.
Updating search and summary scopes. Closes #27.

fix scopes
Roll single-provider.json into registry-hosted providers.json. Closes #28.
Added introspection URI to providers discovery. Closes  #33.