A state lawmaker is proposing penalties, including possible firing, for police officers who swear or use racial slurs in public dealings.   Another lawmaker tells the Boston Herald he's backing Benjamin Swan's measure because police are public servants and the language is unprofessional.  Swan says this is not the first time that he has filed the bill.  He has for the last sixteen years.  He says the law is needed because some cops in some communities do not follow their own codes of conduct.