Restaurants see no shortage of demands for customization and demanding customers, with the latter uttering the former with surprising frequency. Dealing with these demands from the demanding is no picnic, but learning to handle them can be. Not in the literal sense in that you're going to sit down in a nice grassy spot with a blanket, basket, some nice cheeses, a bottle of prosecco, some ripe fruit, and your favorite pal—more so in the sense that like a picnic is a pleasing and relaxing experie…