To test:
1. Check no regressions on Add/Edit/Save items
2. Update translation files for a language,
check new strings "Tag editor" & "No popup" on staff PO file
3. Check it passes xt/tt_valid.t
Patch partially rebased, part rewritten.
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl> Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org> Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>