CDAP-589 Example of service discovery from MR

Updated PurchaseApp to add UserProfile service and demonstrate its use from MR.
Its not necessary to have a function only when you call the same code again. But anyways its a personal preference :)

All it will take is to select the lines of code here press cmd+alt+shift+t and choose method in the refactor menu. Intellij will do all the work for you :)