move Sample,Group to systUtils
WeightVariations: drop _ from leaf names
plot_emu, systUtils: major update

Update these script and functions to work with the systematics.
In particular I am now storing the fake systematic variations
as weight variations in the nominal ntuple from MatrixPrediction.
systUtils add setHistErrFromErrBand
rootUtils add topLeftLegend
plot_emu_mue_fake_ratio: major update, add syst
utils: add print_running_conditions
plot_emu: use utils.print_running_conditions