task/us93-ta68 -- Returns comms trigger (update 3)

nparcel/commsdaemon.py
* new attribute controlled_templates that lists
* update the _start() method to build a list of comms events files on
  a combination if controlled_templates and uncontrolled_templates
* update the comms_kwargs property to include a list of
  template_tokens and returns_templates

nparcel/comms.py
* new attribute template_tokens list of template tokens that are
  currently supported
* refactor the parse_comms_filename() method so that all template
  tokens are configurable and we removed the hardwired dependency
  within the code
* new attribute returns_template_tokens that is a list of template
  tokens that extracts template detail from the RETURNS table
* refactor the get_agent_details() method so that the new template_token
  parameter value can control which table is used to build template
  detail