task/ta-npe-002-21 -- npcommsd controller

nparcel/b2cconfig.py
* new attribute comms_loop

nparcel/conf/nparceld.conf
* placeholder for new comms_loop config option

nparcel/comms.py
* process() method now processes a single comms file per iteration

nparcel/commsdaemon.py
* new method _start() to handle daemonisation
task/ta-npe-002-21 -- npcommsd controller

* round-out the tests