Peel shrimp, and devein, if desired. Saute chopped onion and garlic in 1 tablespoon hot oil in a Dutch oven until tender. Add 6 cups water and next 3 ingredients; bring mixture to a boil. Add pasta; cover, reduce heat, and simmer 12 minutes. Stir in shrimp. Cover and simmer 5 minutes or until shrimp turn pink; remove from heat. Drain and cool 10 minutes. Stir in black beans and next 3 ingredients. Whisk together 1/4 cup oil and lime juice. Pour over salad, and toss. Serve immediately, or cover and chill.