Bug 28353: Display a list of items that cannot be deleted

Bug 28353: Display a list of items that cannot be deleted

We used to display a list of items that cannot be deleted (checked out
or on hold) on the Batch item deletion tool.
With bug 8132 we improve the error handling, but the info is spread in
the table.

This patch adds, at the top of the page, the list of items (barcode)
that cannot be removed.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>