Add support for arbitrary statistics handling and plotting in the `perfprof` executable

[dparo]

Refactor the perfprof code to handle arbitrary statistics from the JSON file

Each statistic should have:

• A stat name
• An associated JSON string entry name for both the BaPCod (if applicable) and for the CPTP json output
• A default value used when the statistic is not found in the JSON file
• A transformation function to create ratios and such for outputting the CSV used for plotting

The CPTP main executable should:

• Expose most of the CPLEX statistics in the JSON output file (examples: number of simplex iterations, number of cuts generated, number of branch and bound nodes, etc)