Bug 26458: Get item details using only itemnumber

Bug 26458: Get item details using only itemnumber

This patch modifies moredetail.pl so that it can accept an itemnumber as
a single parameter.

To test, apply the patch and view a bibliographic record in the
catalog which has one or more items.

 - In the table showing holdings, click the barcode to view the item
   detail page for that item.
 - In the location bar, modify the URL so that it uses only the
   itemnumber parameter, e.g.

   /cgi-bin/koha/catalogue/moredetail.pl?itemnumber=1234

   The page should load correctly, showing information about just that
   item.

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>