task/ta-npe-002-21 -- factor our common daemoniser functionality

doc/source/modules/based.rst
nparcel/based.py
* new files supporting new common daemoniser functionality

nparcel/based.py
* add npcommsd to the package build

nparcel/utils/conf/log.conf
* support for the comms daemoniser logging

nparcel/bin/npcomms
nparcel/bin/nploaderd
nparcel/bin/npprimaryelectd
* use new BaseD()

nparcel/reminder.py
* add support for hold_period attribute