JSA::WrapDR: correct drparameters error message
JSA::Command: preserve -1 status if command missing

Adjusted the behavior of run_star_command so that it continues
to raise JSA::Error::StarlinkCommand in this case (status -1 as
well as status 1).
jsawrapdr: attempt to capture converted log files

convert_log_files now reports the number of converted logs
written.  If there are any then jsawrapdr now calls
capture_log_files, which should in turn invoke the jcmt2vos
script if "persist" mode is on.