By GEIR MOULSON, Associated Press BERLIN (AP) — Chancellor Angela Merkel's center-right party is choosing a new leader this weekend, a decision that will help shape German voters' choice of her successor at the helm of the European Union's biggest economy after her 16-year tenure. Merkel, now 66, has steered Germany, and Europe, through a series of crises since she took office in 2005. But she said