Trigger SF plot with systematic variations

Created by: mmarchegiani

A dedicated library and script are implemented to compute the data and MC trigger efficiencies and SF, and produce plots that are stored in the output directory. The SF are plotted with their statistical uncertainty and the systematic variations for given systematic effects are also evaluated and plotted together with the nominal value. In a future PR also the difference between the Up/Down variations and the nominal SF value will be included in the plots.