Swagger editor update

Right now our API browser uses swagger-editor v 3.0.10, which doesn't support OpenAPI 3.0 and (more importantly) is more than 4 years old. Swagger v.4.0 is realeasing soon, it might be a good idea to upgrade when it is ready. Additionally: we should consider replacing swagger-editor with swagger-ui (which skips the editor pane and is an API viewer only).