Fix iterdays ignoring tzinfo for datetime objects
Fix iterdays ignoring tzinfo for datetime objects

Also add earliest and latest datetime helpers

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