Zero pad report numbers when running multiple reports so the sort correctly on the summary page
Right now if you use the report command to compare directories, they output will be put into directories like "report-0-CG_ABI-L2-CODDM1-M6_G16_s20191471800485_e20191471800554_c20201761959040" or "report-16-CG_ABI-L2-NAVM1-M6_G16_s20191471800485_e20191471800554_c20201761959040". Because my numbers are not zero padded, if you compare more than 9 reports, the resulting directories will sort badly on the summary.html page.
If we zero pad the number in the directory name, they should sort more gracefully. Ideally we should zero pad based on how many total reports we expect to make (so only add zeros to pad when needed).