[FIX] iCal timezones
[FIX] iCal timezones

 - added timezone definition in ICS file;
 - daylight saving time was taken into consideration;
 - addresses #397;

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