LP#1356477: business logic for email checking receipts

LP#1356477: business logic for email checking receipts

This patch adds two methods, open-ils.circ.checkout.batch_notify
and open-ils.circ.checkout.batch_notify.session, that when passed
a set of circulation IDs, creates A/T events for the
checkout notification hooks. In the specific case of the email
checkout receipts feature, the seed data contains a stock
event that would send out emails, but it is conceivable
that other forms of notification could be done by defining
A/T events appropriately.

Signed-off-by: Mike Rylander <miker@esilibrary.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>