[FIX] iCal export for VS breaking with alarms
[FIX] iCal export for VS breaking with alarms

* iCalendar 3.0 needed timedelta instead of iCal syntax string
* Alarm is now child of event, not attached to root of calendar

ThiefMaster/indico,pferreir/indico,ThiefMaster/indico,OmeGak/indico,indico/indico,indico/indico,DirkHoffmann/indico,pferreir/indico,mic4ael/indico,OmeGak/indico,ThiefMaster/indico,mic4ael/indico,mvidalgarcia/indico,mvidalgarcia/indico,mic4ael/indico,mvidalgarcia/indico,ThiefMaster/indico,DirkHoffmann/indico,mic4ael/indico,indico/indico,DirkHoffmann/indico,pferreir/indico,OmeGak/indico,DirkHoffmann/indico,mvidalgarcia/indico,indico/indico,OmeGak/indico,pferreir/indico