What's New Digest 5.3.1

Minor change for XF2.2 backwards compatibility. Only required if running XF2.2 - anyone running XF2.3 can skip this upgrade if you choose.

• bugfix: user preference field in AdminCP wasn't showing in XF 2.3 due to template modifications that no longer worked - this has been fixed
• bugfix: unsubscribe uses stopAllExcept by default in XF 2.3 - so we need to ensure we're stopping Whats New Digest if this is called instead of StopAll
• update test tool to allow sending test emails to a specific user - and handling no threads

Updated test tool now allows you to choose a user to receive a test email digest - which means you can use a test user to validate that unsubscribe options are working as expected.

update helper_account template modification to work with both XF2.3 and earlier versions
listen for sparkpostmail_non_transactional_stop_map event and use the whatsnewdigest email stopper
tweak unsubscribe confirmation message
separate out getMail function so we can over-ride it and add functionality