Bug 11500: Use dateformat syspref and datepicker on additems.pl (and other item catal...

Bug 11500: Use dateformat syspref and datepicker on additems.pl (and other item cataloguing pages)

This patch modifies the cataloging plugin dateaccessioned.pl so that it
triggers the addition of a datepicker widget to fields it is linked
with. Despite its name the plugin can be used on any item field which
requires a date.

To test, apply the patch and make sure you have one or more item
subfields linked to the dateaccessioned.pl plugin. For instance, in
MARC21:

 - Administration -> MARC bibliographic framework -> MARC structure ->
   952 -> Edit subfields:
   - subfields d ("Date acquired") and w ("Price effective from"):
     - Other options -> Plugin -> dateaccessioned.pl

 - Go to cataloging and add or edit an item on a bibliographic record
 - The "Date acquired" and "Price effective from" fields should be
   styled as datepickers.
 - Clicking in these fields should populate the field with today's date
   and trigger the datepicker popup.
 - Test that all the datepicker features work correctly.
 - Test that manual entry of a date works.

 - With the AcqCreateItem system preference set to "placing an order,"
   go to Acquisitions -> Vendor -> Add to basket.
   - Add a title to your basket using your preferred method.
   - In the "New order" form, find the section for adding an item.
   - Test the "Date acquired" and "Price effective from" fields, which
     should behave just like they did in the cataloging module.

Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>