Document APIcast production and staging URL scheme change

Document that the APIcast routes can now HTTP or HTTPS scheme are taking into account when changing the staging or production public base URL: Product > Integration > Settings

However due to OpenShift router limitation, the port are not taken into account on OpenShift side unless ROUTER_SERVICE_HTTP_PORT and ROUTER_SERVICE_HTTPS_PORT are defined correctly.

See https://docs.openshift.com/container-platform/3.11/architecture/networking/routes.html