Make enum select field more powerful
Make enum select field more powerful

- allow "nothing" option
- allow including/excluding certain set values

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