Attendees can only modify own event instance and own PARTSTAT on all attendees' insta...

Attendees can only modify own event instance and own PARTSTAT on all attendees' instances. Lookup event upon incoming scheduling messages in ANY calendar, not just the default schedule calendar.

Hi,

this proposed patch does the following:

- When an attendee (not the organizer) modifies an object, these modifications should be applied completely to that user's instance of the object. However, the organizer's and other attendees' instances should not be modified in most aspects: Only the attendee's own PARTSTAT modification should be distributed to the organizer's and other attendees' instances. E.g. modifications on VALARMs or TRANSP settings are individual to that single user that sends the modification.
  However, I have doubts whether the organizer should be able to apply such modifications on all attendees' instances, once they exist for other attendees. Currently, I did not yet change this behavior.

- When a user receives an invitation in his schedule-default-calendar, he might move it to another calendar. When a subsequent modification to the event arrives, another instance (with the same UID!), is created in the schedule-default-calendar. This patch makes the server search for an instance of the event in any of the receiving user's calendar, so that no event duplicates are created.

I am not really familiar with the code as a whole, so that the way I implemented these changes is probably not "correct".

Regards,

 -frank