Generate summary tables for jointcal/meas_mosaic comparison

Building on validate_drp/reportPerformance.py, we need some code to take the JSON output of validate_drp on all of the tracts+filter combinations and produce some kind of summary table to compare the 115 tract+filter combinations across the three runs (singleFrame/jointcal/meas_mosaic) in photometry and astrometry. There's already some pretty-printing code in validate_drp that we can probably steal.