Bug 28153: Add 'Hold reminder' messaging preference

Bug 28153: Add 'Hold reminder' messaging preference

This adds a new preference for patrons to choose how they wish to receive
'Hold reminder' notices.

The notice is always digested per branch

To test:
 1 - Apply patches
 2 - Update database
 3 - Ensure EnhancedMessagingPreferences and EnhancedMessagingPreferencesOPAC are enabled
 4 - View a patron and note new messaging preference
 5 - Confirm same on the opac for a patron account
 6 - All transports should be disabled by default
 7 - Place a hold for the patron and check it in to confirm
 8 - Run hold reminder script
    perl misc/cronjobs/holds_reminder.pl -v -c
 9 - No message should be queued for patron
10 - Enable the message in a transport for which 'HOLD_REMINDER' notice has content for the patron
11 - Run the script
12 - Patron should have a message queued
13 - Ensure a different transport has content for the notice
14 - Run the script forcing a transport
   perl misc/cronjobs/holds_reminder.pl -v -c -mtt=print
15 - The patron should have a message queued in the forced transport

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>