COPENHAGEN (Reuters) - Gangs of rioters set fire to cars and garbage trucks in northern Copenhagen on Friday, the sixth night of rioting and vandalism that has spread from the capital to other Danish cities, police said on Saturday.Five youths were arrested in the capital on Friday after 28 cars and 35 garbage trucks were burned, Copenhagen police duty officer Jakob Kristensen told Reuters. Danish media said arrests in other towns brought to 29 the number of people police were holding. Scores of cars and several schools have been vandalized or burned in the past week. Police could give no...