Bug 26619: Cart - The "Print" button is only translated when you are in "More details...

Bug 26619: Cart - The "Print" button is only translated when you are in "More details" mode

This patch adds the "Print" string to datatables.js so that it can be
picked up for translation.

To test, apply the patch and add some items to the cart in the OPAC.

- Open the cart. You should see a button labeled "Print."
- The print button should work correctly.

TESTING TRANSLATABILITY

- Update a translation, e.g. fr-FR:

  > cd misc/translator
  > perl translate update fr-FR

- Open the corresponding .po file for JavaScript strings,
  misc/translator/po/fr-FR-messages-js.po
- Locate strings pulled from
  koha-tmpl/opac-tmpl/bootstrap/js/datatables.js for translation:

  msgid "Print"
  msgstr ""

- Edit the "msgstr" string however you want (it's just for testing).
- Install the updated translation:

   > perl translate install fr-FR

- Switch to your newly translated language in the OPAC and
  repeat the test plan above. The translated strings should appear.

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>