Mc12345678 mixed

This needs some testing; however, conceptually, the two files modified below (includes/modules/pages/shopping_cart/header_php.php and includes/modules/pages/checkout_shipping/header_php.php) have been revised to allow products to have attributes, but not be tracked by SBA and yet if they have mixed content then to be handled by ZC as they originally were intended...  The code is cleaner on the checkout_shipping section and considered more "reliable".  The response for the shopping_cart needs some testing.  Ie., please help out here with verification of functionality and response.