task/ta22-25 -- exporter should not write file if no collected items are
detected

nparcel/bin/npexporterd
nparcel/bin/nploaderd
* pidfile now writes to the ~/.nparceld directory

nparcel/dbsession.py
* subtle formatting mod to the ISO time

nparcel/exporter.py
* extensive mods to bypass report write if no collected items are
  detected

nparcel/exporterdaemon.py
* update the _start() method to handle the new processing workflow of
  Exporter()