General Motors plans to cut 500 car dealers from its dealership network in the U.S.  The automaker is dropping Pontiac, and trying to sell Saturn, Saab and Hummer by the end of the year.  As the Nashville Business Journal reports,  Local car dealers are waiting for word on what's next in their uneasy marriage with GM.  The car company is scrambling to survive with a $15.4 million federal bailout, and has just one month to reorganize, under pressure from the White House.