It's a butterfly knife, Charlie Brown...At yesterday's SFPD press conference, Chief George Gascon -- he of the nifty suit -- appears to have dressed as a police officer for Halloween. You can, too -- but if you tote a weapon, stumble drunkenly through public thoroughfares, urinate or defecate in public, Gascon promised that San Francisco Police will have zero tolerance. Well, to borrow a phrase from another holiday, "Why is this night different from all other nights?"Following a shooting that