First it was Subway with its $5 foot-longs and annoying jingles to match. Then Quizno's followed with a copycat $5 menu before getting even more aggressive with a $4 sub. After that, the floodgates opened and Boston Market and Shoney's tried $5 specials. Now T.G.I. Friday's joins the list.For the 31 days of May, 16 sandwiches and salads at the fast-casual chain will be just five bones. That's not just lunch but the dinner price, too. Sandwiches include the California chicken club, the barbecued