See all alerts (including those not in common) when batch editing item alerts

[Stephanie Leary]

Branching off bug 2012971, based on Tiffany's comment at #10 there:

When batch editing items that have alerts, the new modal dialog shows only the alerts shared by all the items in the batch (specifically comparing: alert type, text, and cleared status). The modal's title bar reads "Managing alerts in common for N item(s)." There is no further indication that some of the items in the batch may have additional alerts.

The modal body should include some indication that there are additional alerts that are not shared by all the items. They should not be editable, but the user should see that they exist.

We need to add a section to the modal body below the editing rows where we list the items (identified by barcodes??) that have additional alerts, and a read-only display of the alert types, text, and temporary status.