A cargo ship carrying thousands of luxury cars has sunk off the Portuguese Azores archipelago, almost two weeks after it caught fire.   The vessel was carrying about 4,000 vehicles made by Volkswagen Group - including Porsches and Bentleys - from Germany to the US. As it was being towed, the Panama-flagged Felicity Ace plummeted due to structural problems caused by the fire and rough seas, according to a port official. Joao Mendes Cabecas, the captain of the neare