Bug 4944: Add OpacNoItemTypeImages system preference

Bug 4944: Add OpacNoItemTypeImages system preference

At the moment noItemTypeImages pref controls staff and OPAC
display. With this patch, there will be a separate OpacNoItemTypes
preference that allows to control display of each separately.

To test:
- Apply patch and run database update
In Administration:
- Search for 'noItemTypes' preferences
- Verify the settings of both prefs match
- Toggle prefs, verify everything works ok
- Go to the item types configuration page
- Try different settings for both prefs:
  - Both set to No: Only a message with a link to the prefs should show
  - Both set to Yes or either set to Yes: image configuration options
    should show
In the OPAC:
- Check the following pages with item-level_itypes = record
  - advanced search
  - detail page
  - place hold page
- Check the following pages with item-level_itypes = item
  - result list
  - a list (opac-shelves)
  - checkouts and overdues tabs in patron account
    (Note: this didn't work right before, but will now.)
  - reading history in patron account

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>