Remove single cut plots

Remove the "truth" and "reco" single cut plots. We leave only plots
generated by ZDefinitions.
Add comments and indetation fixes to ZFinder.cc

Add comments on the z_fitter, which is the code that makes
RooWorkspaces.
Add fit_mc_to_signal.cpp

fit_mc_to_signal.cpp takes two histograms, a data one and an mc one,
normalizes the area of the mc to match the data, and plots the data as
points over the mc.