LP#1666512 - Only insert if not already existing

LP#1666512 - Only insert if not already existing

This repatch was requested by Galen Charlton to make it easier for
upgrades to avoid adding the entries or failing if the entries already
existed.

Also drops the unnecessary i18n tagging for the billing type names
since it does not work with applying upgrade scripts (only for sourcing
db.seed data for translation to PO file)

Signed-off-by: Ben Shum <ben@evergreener.net>
Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>