Update Chapter 11 to Watson Discovery

Chapter 11 has been simplified and updated, replacing Retrieve and Rank with Watson Discovery. Because of all of the services offered with Watson Discovery, the user experience is vastly simplified and most of the work to configure, upload and train Watson Discovery is now done through the IBM Cloud Web interface.

There is a new ReadMe file for this chapter which explains how to use Discovery, the process to upload and train and the small amount of code now required to support a query interface to Discovery.