- sending alarms to CalDAV/GroupDAV clients as offset, not fixed time like before
- only exception to the above are alarms for recuring events to Lightning, which must be absolute, as offset lead to infinit poping up alarms in Lightning
- update all alarm times of other users alarms too, when storing events, as they might not be included in the stored event
(changed quantity was used for conflict check, but not stored!)
There is still a bug with multiple non-overlapping events overlapping the checked event: check is against quantity sum, not the maximum
