Fix schema, clarify spec (v1.1.0)

[m-mohr]

I started with a faulty schema (no Catalog support) and then came across more inconsistencies and ambiguities, so I decided to give this a rework.
I hope the changes reflect the actual intended behavior, some things were hard to understand.

Changed

• Split Authentication Flows Object into OAuth2 Flow Object and Signed URL Object
• The JSON Schema is much stricter compared to before, actually enforcing many restrictions documented in the written spec
• The Parameter Schemas must comply to JSON Schema draft-07 instead of OpenAPI Schema, fixes How to define the parameter schema  #21

Fixed

• JSON Schema supports Catalogs
• Fixed various issues in the JSON Schema
• Clarified which fields apply to which schema type
• Clarified required fields
• Fixed examples

Additionally, I'd love to also clean up #30 but that might be too much of an ask for now.

PS: The schema is pretty complex and I hope everything works as expected, but no guarantee ;-)

[jamesfisher-geo]

Looks good. Thanks.

I added a PR #32 to remove the provider specific types in this branch.