#16 calendar participants link should be present for new events

[Robert D. Zeigler]

Currently, to change the participants for a new
calendar event, you have to first create the event,save
it, then reopen it for editing. It would be nice if the
participants were initially editable. This could be
accomplished by creating the event initially and not
comitting changes until the event is saved (and
deleting the event if the operation is cancelled).