Payment Method admin settings

Hey Alexis,

Love the simplicity and utility of this module. I have attached a patch with an 'op': 'settings' section for the uc_test_payment_method function. No functionality changes, just this info/help section/pane to be added to the Payment Methods tab page in Store Admin. Adding this settings section makes it a bit more explicit how to use and configure this module. In addition, I remind folks to delete Test Payment transactions in a live site to keep a store's data clean.

Thanks again,
--Sohodojo Jim--