title: Adding processes in payment pipeline in ATG
body: <p>i am atg beginner </p>
  
  <p>I have to add few processes to payment pipeline(paymentpipeline.xml) as I have to do some integration stuff. Please let me know how to add processes to payment pipeline and how to invoke them ? 
  Also, i am not able to find paymentpipeline.xml in my project. Do i need to create it or do changes in commercepipeline.xml? Thanks</p>