With gun ownership on the rise and the numbers of those with concealed carry permits exploding, a new poll shows that Americans are ready to use those weapons if threatened.In a survey for Insurancequotes.com, 78 percent said that they are mentally and physically prepared to kill an intruder. And even those armed with less lethal weapons, such as pepper spray or a golf club, would kill if they had to.  Some 44 percent of homes have a gun, according to the Pew Research Center.The thrust of the survey was to see how well prepared Americans are to handle an...