fix the error message after complete payment. Add new feature "Express checkout".
bug fixed: 1,"Notice: Undefined variable: details in uc_payment_method_alipay() (line 85 of D:\xx\uc_alipay.module)." 2，“Notice: Undefined index: pay_method in uc_payment_method_alipay() (line 88 of D:\xx\uc_alipay.module) and other bugs
dev version with latest changes.
First workable version for drupal 7, 本模块用的是支付宝的即时支付接口.
drupal6, Ubercart2.x
