LP1883171 & LP1940663: Replace circ method to update latest inventory

LP1883171 & LP1940663: Replace circ method to update latest inventory

Replace the open-ils.circ.circulation.update_latest_inventory method
with open-ils.circ.circulation.update_copy_inventory.

Beyond renaming the method and changing the tables it operates on, the
following changes are also made:

1. Use savepoints to allow some updates to succeed when others fail.

2. Modify the return value to include success and failure counts so that
these could potentially be used in client feedback.

This work was sponsored by NOBLE.

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