Add wpsc_checkout instance as parameter to checkout loop actions.
In WPSC_Purchase_Log::get_cart_contents(), return cart contents if it is not empty.
Fix some weird formatting from the product add/edit UI remix.
Use proper WP warning/notice conventions for tax notices.  Also, effect !== affect.
JS copypasta was causing spinner to not be shown when selecting shipping module settings.
WP-e-Commerce javascript updates

* Check so that we don't start the process of getting the customer meta unless there are HTML elements where it would be displayed

* Check the get customer meta return structure to be sure that elements being retrieved are present before accessing them, avoid js warnings when elements not present
Merge remote-tracking branch 'origin/pr-js-tuning' into dev-master