Integrate Mark M.-provided D1.8 code

[DrDeke]

Mark M. wrote some excellent code that would compute D1.8 retrospective rates based on a worst-case assumption that DTE called the maximum allowed number of CPP/DPP events, and that the events occurred during your highest-usage periods for the year. He gave me permission to add this code to the script, but I have not gotten around to it yet. This would be an excellent addition.