By Katharine Houreld KARACHI (Reuters) - Pakistan's chaotic financial heart is home to 18 million people, Taliban bombers, contract killers - and one of the world's most successful stock markets. With 49 percent returns in 2012, the Karachi Stock Exchange (KSE) was one of the five best performing markets in the world. Now it is seeking a foreign partner to buy a stake and take over management of a market that has risen three-fold over the past four years. ...