If you frequent Dupont or Logan circles, please note those traffic circles are tied to the apex of all evil: The White House. That’s what people who push Masonic conspiracy theories would like to make you to believe at least. Now that “DaVinci Code” author Dan Brown is preparing his next megaseller on D.C.’s Masonic machinations, we thought we’d lay out the general thought patterns as to why some people think the L’Enfant street plan…