jsawrapdr: make failure to read files fatal
jsawrapdr: show output from dpRetreive
jsawrapdr: raise an error if files are missing

Check that dpRetrieve actually retrieved the correct number
of files.
jsawrapdr: unzip any retrieved gzipped files
jsawrapdr: add --debugxfer option to debug capture

This causes listings to be printed before and after cleanup,
and of the transdir after capture (if specfied).