Rewrite and fix event menu creation/refresh logic
Rewrite and fix event menu creation/refresh logic

Now missing child menu entries are properly created

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