task/us79-ta12 -- T1250 agent code filtering should be a configurable
item

nparcel/conf/nparceld.conf
nparcel/b2cconfig.py
* new attribute "filtering_rules" which is a list of tokens to match
  against the start of the agent code field during the Delivery
  Partner filtering process
task/us79-ta14 -- Integrate the new filtering_rules config item into
filter.py

nparcel/filter.py
* updated the process() method to support configurable list of tokens to
  filter agent codes against
* new __init__() method to handle initialisation of the filtering_rules

nparcel/filter.py
* update _start() method so that call to parcel.Filter() passes through
  the configured filtering_rules