PayPal Pro Direct Payments & Express Checkout

[michael_s]

This is mainly a maintenance release, but here are the updates:

* Readded UK features since PayPal still supports it through the US API.
* Fixed the quantity in order list bug (Thanks to Glen aka Steve Dallas)
* Removed old unused code remnants
* Fixed a zone query bug that would return incorrect state abbreviations
* Updated the wpp_diagnostics file to correctly show curl errors and stop the test if any are encountered.
* Added the Express Checkout button on the shopping_cart.php page.

PLEASE STOP POSTING PAYPAL'S OFFICIAL VERSION HERE AND INSTEAD UPLOAD IT AS A NEW CONTRIBUTION IN ITS OWN SPACE.

Their official version is based off of 0.7.3 of this module, but the two forks are no longer anything alike so there's no reason to post it here other than to confuse users who don't know which one to use.

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