move integralAndError to rootUtils
systUtils: refactor computeFakeSysErr2 -> computeFakeSysStatErr2 (sometimes need to only add syst)
reimplement buildStatisticalErrorBand; add buildSystematicErrorBand, combineStatAndSystErrorBands
check_hft_trees: also plot sys, stat, and combined error band
define systUtils.totalUpDownVariation; typo in combineStatAndSystErrorBands
systUitls: rename a few functions, improve docstrings
check_hft_trees: filter syst from cmd-line option, and pass these to buildSyst
add option to fill in batch (along with template)