Initial commit of Materialize Client example.

[julianleonard123]

This is Java client app that calls LookupPermissionSets, consumes the events in pages, counts the events consumed, and then starts WatchPermissionSets.

It shows how to interact with the Materialize APIs.

It writes the cursor to a file.

Future Improvement:

Add re-start logic that can use the cursor in the file in case of connection drop / interruption / errors.