Bug 12084: Format planned date in publication details on detail page

Bug 12084: Format planned date in publication details on detail page

If items are created for a serial subscription, the issue
information is shown on the details page in staff with the
planned date in ().

To test:
1) Create a subscription with items added on receive
2) Receive a few issues and create items
3) Check the staff detail page
4) Verify that the published date shows under Publication details
   in the items table, but that the date is not formatted
5) Apply patch
6) Verify the date is now formatted according to the DateFormat
   system preference setting

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>