added functions adjust_overflow_to_limit & clean_control_region
added get_best_max_y and get_best_min_y functions to tools/plotting.py
 - updated fitting and plotting scripts for the new fit variables
 - added closure test and closure test type options to fitting script
 - added no_combined_signal option to fitting script
 - added test option to fitting script (just central measurement)
 - added disable-constraints option to fitting script
more control plots for the fit variables
moved closure test definitions here, addded JSON read functions for fit results
added commands to run & plot the fit checks