Add pgtap tests for schema and data changes.

Add pgtap tests for schema and data changes.

These tests only check that org_unit settings were properly added,
that the new money.void_payment table, its indexes and triggers were
created, that three columns were dropped from the money.billing
table, and that three functions exist.

Other tests for the view changes require test data and are beyond my
pgtap fu at the moment.  They will have to be added later.

Signed-off-by: Jason Stephenson <jason@sigio.com>