Crude Oil Prices Top \$50 Per Barrel LONDON - Crude oil topped the psychological milestone of \$50 per barrel Tuesday for the first time, and a Saudi Arabian oil official said the world's largest petroleum exporter would raise its production capacity by nearly 5 percent in a bid to calm prices.    Analysts said instability in the Middle East, political unrest in Nigeria, Africa's top oil exporter, and damage to U.S...