Exception dates are "recreated" when "editing all repetitions" after deleting one

[klickagent]

Reproduce: • Create daily "Meeting" repeating event at 10:00 - 11:00 • Remove one event* of the recurring "Meeting" event • Edit using "editing all repetitions" and set start date to 10:30

Expected behaviour: Removed event should stay "removed"

Current behaviour: Removed event reappears

In addition: If you move all events back to 10:00 (startime) using "editing all repetitions": The event* gets removed again.

[klickagent]

The reason for it lies in the EXDATE implementation (it holds the start date, and needs to be shifted as well when moving the entry!