Pileup awareness in JetMonitoring

First attempt to include pileup (and other EventInfo) variables into the JetMonitoring Tool, such that we can use it for event selection in the config, e.g. plotting jet variables for low Mu vs. high Mu events. Could potentially be extended to create 2D plots (e.g. pt vs mu), hence the additional EventVariable class.

Tagging @jbossios and @delsart