Update registry client implementation to integrate with uor-zot implementation

[jpower432]

What is the problem you're trying to solve

The emporous client does not integrate the the endpoint created in the uor-zot implementation.

Describe the solution you'd like
The emporous-go implementation need to integration with the uor-zot implementation for proper support from a registry.

Additional context

• All references to the collection spec should be replaced with the Statement spec from uor-zot -> https://github.com/search?q=repo%3Aortelius%2Femporous-go%20collection-spec&type=code.
• Possibly archive the collection-spec repository.
• Rename the Collection type to Statement (?)