add twistedcaldav.directory.test.test_directory.DirectoryRecordTests.test_attendee and fix DirectoryRecord.attendee()


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11944 e27351fd-9f3e-4f54-a53b-843176b1656c
Switch notifications to be stored as JSON in the DB but re-written to XML in the app.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11945 e27351fd-9f3e-4f54-a53b-843176b1656c