first step for CalDAV scheduling

- principal reports scheduling-inbox-URL /<username>/inbox/ and scheduling-outbox-URL /<username>/outbox/
- outbox collection contains no events
- outbox correctly answers POST for freebusy information
- outbox respons to all other POST with "204 No Content", ignore client request to deliver invitations
- inbox collection contains events of unknown status (PARTSTAT=NEEDS-ACTION)
- inbox responds to DELETE with "200 Ok"
--> iCal under OS X now shows freebusy times :-)
(had to add "write-content" privilege for calendar collections user has edit rights for, to allow adding events)

phpgwapi/inc/class.groupdav_handler.inc.php

@@ -412,6 +412,10 @@ abstract class groupdav_handler
 			$priviledes[] = 'bind';	// PUT for new resources
 		}
 		if (!$user || $grants[$user] & EGW_ACL_EDIT)
+		{
+			$priviledes[] = 'write-content';	// otherwise iOS calendar does not allow to add events
+		}
+		if (!$user || $grants[$user] & EGW_ACL_DELETE)
 		{
 			$priviledes[] = 'unbind';	// DELETE
 		}