task/ta-npi-016-07 -- barcode, connote or item_number raises exception
if empty

nparcel/loader.py
* set_default_equals() method had a bug which was unconditionally
  raising exceptions if condition flag was set
* made connote a required field

nparcel/tests/__init__.py
nparcel/tests/test_loader_ipec.py
* new Ipec-specific test cases