[IMP] Allow plugins to be notified themselves of event date changes
[IMP] Allow plugins to be notified themselves of event date changes

 - Their CSBooking class must implement a notifyEventDateChanges method.
 - Changed a Logger.error to Logger.exception

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