Add HitsDecorator class

This adds a skeleton class to add hit information to jets. It's intended as a starting point for more interesting trackless b-tagging studies. Probably of interest to @awesten, @thuffman, and @sargyrop.

This should change nothing in most cases. The hit containers aren't usually stored in AODs, so I've add an option that decorates these to jets. It's off in every case except in the new configuration I created, which is called TracklessEMPFlow.json.