The nonpublic note for items is not displayed in the staff client. It
should be displayed in the following areas:
1) Checkouts (circulation.pl)
2) Checkins (returns.pl)
3) Record details ( moredetail.pl )

Test Plan:
1) Ensure your non-public note field is mapped to the
   items.itemnotes_nonpublic database column
2) Edit an item, add a test nonpublic note
3) Check out the item, verify the note is visible in the checkouts table
4) Check in the item, verify the note is visible in the checkins table
5) View the item details, verify the note is visible and editable
   if your account has the rights to edit items

Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>