CORE-5832 Refactor success and error responses.

Removed the "success", "status", and "action" keys from JSON responses.
Refactored metadactyl's swagger-response into the success-response function.
CORE-5832 Rearranged new endpoint order.

New endpoints are now ordered by URI, then by HTTP Method.
Also removed obsolete 'get-app' endpoints and docs in metadactyl.