task/us93-ta68 -- Returns comms trigger (update 2)

nparcel/commsdaemon.py
* new attribute controlled_templates list of comms templates that are
  controlled by the delivery period thresholds
* refactor the get_comms_files() method to use the
  nparcel.utils.files.get_directory_files_list() function
* refactor the _start() method so that it can selectively invoke
  get_comms_files() based on templates provided by
  controlled_templates attribute
* integrate reporting so that each iteration presents a stats
  log item