THERMOSTATICALLY-CONTROLLED ELECTRIC WARMING AND SERVING EQUIPMENT, NAMELY, FOOD CONTAINERS, CASES, AND FOOD CARRYING CONTAINERS HAVING AN ELECTRICALLY CONTROLLED HEATING ELEMENT AND A THERMOSTATIC SETTING FOR THE SERVICE OF FOOD IN INSTITUTIONAL AND INDUSTRIAL SERVICE SECTORS, NAMELY, HOSPITALS, SCHOOLS, RESTAURANTS, FAST FOOD FACILITIES, PRISONS AND OTHER INSTITUTIONAL FACILITIES