Bug 10907: Optionally show the staff member's name who managed a suggestion in OPAC

Bug 10907: Optionally show the staff member's name who managed a suggestion in OPAC

The name of a staff member who managed a suggestion is shown in the
the OPAC if the new system preference OpacSuggestionManagedBy is set to
'Show'. This is also the default.

If the preference is set to 'Don't show' the staff members name
is not displayed and the column 'Managed by' in the table of
suggestions in the patron account is not displayed.

To test:
- Create a one or more suggestions
- 'Manage' them by accecpting or rejecting
- Go to your patron account and check that the staff member name is
  shown for your suggestions
- Apply patch, run database update
- Check the name is still shown
- Switch the preference to 'Don't show'
- Check the name is no longer shown and the table still displays
  correctly, but without the 'Managed by' column
- Repeat those tests for both bootstrap and prog theme!

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Works as advertised, the only little nitpick is you could just do
[% IF Koha.Preference( 'OpacSuggestionManagedBy' ) %]

However you are following the custom in that file already, so that's
fine

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>