Worldpay: Use updated address format

The original handling of address was added to Worldpay in April, 2011.
In September, 2011, Worldpay updated their API and changed some of the
names of the fields used:

http://support.worldpay.com/support/gg/index.php?page=news&sub=payment-page-changes-details-sep2011

The old fields still work (for now).  Even so, the new fields simplify
our logic some and make things more consistent with their current API
docs:

http://support.worldpay.com/support/kb/gg/pdf/dxml.pdf

Those docs no longer even refer to houseName, houseNumber, or street
fields.