PIDCalib Fit-And-Count Modifications

Various modifications to the PIDCalib fit-and-count tool:

• Can now use an arbitrary number of dimensions for the efficiency histogram binning. The class of ROOT histogram containing efficiency information is automatically selected, depending on the number of binning variables which are specified.
• Conditions specifying whether to save efficiency values in each bin (checking the uncertainty on the efficiency is below a certain threshold, or the number of events passing/failing the PID cut are above zero in that bin, etc.) are no longer hard-coded in computeEff.py. Instead, they are given in the config YAML file.
• An example config YAML file, using the new syntax for saving conditions and binning schemes, is provided in config_test/RK_ID_11_0_Brem.yaml.
• Some general re-factoring of code, wrapping more stuff into functions, and adding more commentary.
• The binning schemes contained in .py files output by the binning optimisation script can be used. The locations of these .py files, and the name of the binning scheme, must be specified in the config YAML file.
• Example YAML files, used for the generation of R(K^+) and R(K^{*0}) efficiency histograms, now use the new syntax.

The efficiency histograms for correctly-identified electrons, with production configured by the YAML files config/RK_ID... and config/Rst_ID... have been compared to those produced using the old script, and are found to be identical.