Bug 27899: Missing description for libraryNotPickupLocation on request.pl

Bug 27899: Missing description for libraryNotPickupLocation on request.pl

This patch adds text to the holds template in the staff client so that
if a particular item is at a library which isn't a hold location the
error message is descriptive.

To test, apply the patch and go to Administration -> Libraries.

 - Change one of your libraries so that "Pickup location" is set to
   "No."
 - Locate a title in the catalog which has an item at that location.
 - The "pick up at" list will exclude the library so and additional steps
     must be taken to get the message
 - Select a patron and set their library to the one we can't pick up at.
 - Start the process of placing a hold on the title.
 - After selecting the patron to place the hold for, look at the table of
   items under "Place a hold on a specific item."
 - The item located at the library you modified should show an error
   message in the "Hold" column, "Library is not a pickup location."

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>