Reminder date tokens should follow date formatting configured by site

Rather than the default MySQL format of 2012-12-01 it should be the format configured by the site at: civicrm/admin/setting/date?reset=1

With guidance from lobo I have edited the Core/BAO/ActionSchedule.php with new elseif{} cases for:
start_date, end_date, activity_date_time and join_date

Start date and end date apply to both events and memberships. I have tested all 3: events, memberships and activity to make sure the tokens work.