task/ta-npi-016-11 -- manufactured barcode should not generate another
job_item lookup in an update scenario

nparcel/loader.py
* process() method has extra smarts to flag if a job_item has been
  identified as part of a current job table check.  Specifically
  during the manufactured barcode check
* update() method signature now includes skip_jobitem_chk argument
  which bypasses jobitem insert check and only updates the job table
  record

nparcel/table/jobitem.py
* new method connote_item_nbr_sql() which generates an SQL wrapper to
  extract records where job_item.connote_nbr is equal to connote and
  job_item.item_nbr equals item_nbr