Add UT track info functors
Add new functors that allow to obtain the clusterCharge (adc) and number of strips (size) of all the UT clusters on the track. In addition, functors that allow to determine the mean and median of a vector of inputs are added.
These functors are needed for new HLT2 lines that select decays into helium-3 (Moore!3279 (merged)). The UT clusters for helium are expected to have (x4) higher ADC values and larger clusters.
Relies on changes to clusters on track (v1) introduced in Moore!2754 (merged).