• Added: calendar-user-address-set to default principal search properties
  list. This should fix iOS attendee autocomplete support.
• Changed: Moved all 'notifications' functionality from Sabre\CalDAV\Plugin
  to a new plugin: Sabre\CalDAV\Notifications\Plugin. If you want to use
  notifications-related functionality, just add this plugin.
• Changed: Accessing the caldav inbox, outbox or notification collection no
  longer triggers getCalendarsForUser() on backends.
• #533: New invites are no longer delivered to taks-only calendars.
• #538: Added calendarObjectChange event.
• Scheduling speedups.
• #539: added afterResponse event. (@joserobleda)
• Deprecated: All the "tableName" constructor arguments for all the PDO
  backends are now deprecated. They still work, but will be removed in the
  next major sabredav version. Every argument that is now deprecated can now
  be accessed as a public property on the respective backends.
• #529: Added getCalendarObjectByUID to PDO backend, speeding up scheduling
  operations on large calendars.