task/ta-npp-001-06 -- copy files to the aggregator directory

nparcel/loaderdaemon.py
* new method aggregate_file() that will attempt to copy file to the
  special
  aggregator directory for further processing
* new helper method distribute_file() that manages post-processing
  file distribution
* updated the process method to support copying of files to the
  aggregator directory

nparcel/utils/files.py
* new function copy_file() that attempts to copy source to target