Make node-red-bluemix-starter be Diego ready

[ibmamnt]

VCAP_APP_PORT is deprecated in Diego. This is a request to change VCAP_APP_PORT to PORT in "bluemix-settings.js" file. PORT should work in current Bluemix (DEA) too ( as of 2016/Oct/11th).

For more information about the change, please refer to this doc.

http://docs.cloudfoundry.org/devguide/deploy-apps/environment-variable.html#VCAP-APP-HOST
and
https://github.com/cloudfoundry/diego-design-notes/blob/master/migrating-to-diego.md