Provider - Add endpoint to review all available layers

As mentioned in the Pre-ship KT session, users would benefit from an ability to review all available layers being served by the Provider without having to: a) Review the koop-config.json b) Query each and every layer starting from 1

There should be an endpoint served out by Koop that will scan the configured layer definitions and list them in a JSON response.

Relevant files:

• ignite-provider/lib/ignite-client.js
• ignite-provider/src/model.js
• ignite-provider/config/koop-config.json

Relevant files for adding new endpoints:

• osdu_gcz_provider/koop/src/routes.js
• osdu_gcz_provider/koop/src/index.js

Bare minimum for layer info: layername and layer URL

See KoopJS docs: http://koopjs.github.io/

Bonus: It would be nice to see feature count for each layer as well included in the response. This would require querying each layer with the returnCountOnly attribute set to true.