USERGRID-2625:

 o Added JobListener interface for callbacks to scheduler
 o Added setters to register JobListener
 o Created TestJobListener utility class for to collect stats
 o Created test case for TestJobListener
 o Used TestJobListener to fix and make deterministic SchedularRuntimeXIT tests
 o Cleaned up a few things here and there and to comply with ASF requirements
 o Added AL 2.0 Headers and removed @author tags
 o Cleaned up imports
 o Added package-info.java files for some packages