LP#1081551 Serials batch recv. dupe barcode check

Exit processing and return an event if the barcode on a new serial.unit
collides with an existing serial.unit or asset.copy barcode in the
serial receive API.

In the UI, detect the dupe barcode event and provide an error message to
the user.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Jennifer Pringle <jpringle@sitka.bclibraries.ca>
Signed-off-by: Ben Shum <bshum@biblio.org>