Factor out handling of filer_id. Add more IEC data.

This should fix #311 issues.
Factor out the handling of filer_id (usually the recipient of a contribution):
   There are committee ids which are not integers, map them to unique integers.
   Make sure we update pending ids when we find them.
Add the IEC info from form 496
Special case Kaplan, since there is an IEC that matches better than her committee.
Update map.csv (early and often).
So here we're creating `Party::Individual` records despite the fact that `row['entity_cd']` is actually 'Other'. What exactly is this getting us?