Mark CalendarEvent.ExceptionRule as obsolete #867
Description
The EXRULE property is explicitly marked as Deprecated in RFC 5545.
Under the Appendix section detailing "Deprecated Features" (A.3), it is stated that the "EXRULE" property can no longer be specified in a component.
Should be marked as obsolete in v5 and get removed in v6.
[Edit]
Supported neither in Google Calendar nor in Microsoft Outlook/Exchange.