LP#1564079 Checkout history handles serials

LP#1564079 Checkout history handles serials

Remove the target_copy foreign key constraint on action.usr_circ_history
so that it does not prevent creation of rows from circulation's that
link to serial.unit objects.  Similar to action.circulation, the foreign
key constraint is enforced via a evergreen.fake_fkey_tgr trigger
instead.

This modifies the 2.9.3-2.10.0-upgrade-db.sql and 0960 upgrade scripts,
since without this change, the scripts may fail.

A separate upgrade script is added to drop the constraint for those who
have already successfully run the the 2.9.3-2.10.0-upgrade-db.sql script
(i.e. those who don't use serials).  For simplicity, the
evergreen.fake_fkey_tgr trigger is only applied in this separate upgrade
script (in addition to the base schema, of course).

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Conflicts:
	Open-ILS/src/sql/Pg/version-upgrade/2.9.3-2.10.0-upgrade-db.sql