True dining bargains are so few and so far between in Paris that by the time you discover a new one, the previous find has usually turned into an old legend that the Elders like to recount around the fire while the Young sit there and wish they'd brought their iPod.But when it comes to lunch and fuss-free food, Paris has no shortage of hole-in-the-wall gems: you just need to know where to look. And today, let us look in the general direction of Belleville and, more precisely, a little...