task/ta-npi-023-11 -- get template parameters

nparcel/conf/npreminder.conf
* new config item "hold_period"

nparcel/reminder.py
* support for new attribute "hold_period"
* new method get_agent_details() which returns agent details based
  on job_item.id

nparcel/table/jobitem.py
* new method job_item_agent_details_sql() that produces a
 SQL string to extract the agent details against a job_item.id