Place the farro in a saucepan and add enough water to cover by one inch. Bring the water to a boil over high heat. Lower the heat, cover the pan, and simmer for about 30 minutes or until the farro is tender. Drain any remaining liquid and place the farro in a bowl to cool. Add the tomatoes, cucumber, kalamata olives, scallions, feta cheese, dill and garlic and toss to distribute ingredients evenly. In a small bowl, whisk the olive oil, red-wine vinegar, lemon juice and mustard. Pour over the salad and toss the ingredients. Add salt and pepper to taste. Let the salad stand at least 30 minutes before serving.