Changes

tsk97 Adds generation of notifications when an event is cancelled or
modified
Modifies EventEJB so that when an event is cancelled or modified, its
attendees receive a notification. It also sends the notification by
email to those attendees who have previously chosen this feature in
their own profile.
Modifies AdminController, AdminEventsController, ModifyEventController,
and EventResource to throw MessagingException, needed by sendEmail.