20110820
========

Continued to work on :srcref:`docs/tickets/47`.

- :term:`watch_calendars` now deletes events in db if they have 
  been deleted from remote calendar.

- New model :class:`lino_xl.lib.cal.AttendanceRole`.
  New field `Attendance.role`.

- New choicelist :class:`lino_xl.lib.cal.utils.AttendanceStatus`.
  New field `Attendance.status`.

- Removed field `Attendance.confirmed`.

Recurrent events are not yet handled at all. 
Check-in 20110820