+ CreatePartnerTradeByBuyer

+ CreatePartnerTradeByBuyer, you can apply if you have register this service.
* Updated sample config file. If you desire new request, it is recommended to update.
* bugfix: fix typo in param list: return_uri -> return_url

In future we will focus on reqs & resps, give out more getBlabla() and setBlabla() to ease construct/parse work.
...If I can struggle for spare time from my boss. Huh.