Localize countries data into checkout page for a faster more responsive checkout experience

* Tune the AJAX response to only send parameters that have changed
* Implementing localized countries for use by WPeC js
* Use jQuery.ajax to provide async meta transactions instead of jQuery.post
* Add countries localization for use by wp-e-commerce.js
* Use JQuery ajax to do async transaction
* removed replacements for meta updates from response
* ajax url wrapper is removed

** Also... **
* Added ability to define meta value defaults for WPSC_Country class meta properties.  Used this new feature to manage the default from "region_label".