Update CheckoutStep_PaymentMethod.php

Make the extend name consistent with the form name.  There is already an extend name "updateConfirmationForm" in the ConfirmationForm function within the CheckoutStep_Summary class.
Update SteppedCheckoutPage.ss

Change the title from "Payment" to "Payment Method" to avoid confusion with the following summary step where the user clicks the button "Proceed to Payment".
Update ShopAccountForm.php

Shift the form's extension to below $this->loadDataFrom($member) so that the values loaded from $member are passed onto 'updateShopAccountForm'.  Thanks.
Merge pull request #293 from AntonyThorpe/patch-2

Update CheckoutStep_PaymentMethod.php
Merge pull request #295 from AntonyThorpe/patch-4

Update ShopAccountForm.php
Merge pull request #294 from AntonyThorpe/patch-3

Update SteppedCheckoutPage.ss