calendar defaults

Hi Daniel,

On today's call we discussed that we'd like to switch the calendar behavior
from tentative to confirmed. Then instead of confirming a tentative invite,
we would cancel a confirmed one. This matches the ARIA WG calendar and
would ensure that the invite shows up more prominently in people's
calendars.

It would also be good if I could update calendar entries, if that's
possible.

Best,
Peter.