Database Upgrade Routine to rename old _wpsc_* product metadata array keys so they no longer include the '_wpsc_' prefix

Fixes #492
Changelog for database upgrade routine
make  an empty array so implode doesn't fail
add wpsc_purchase_log_csv hook so we can do fun stuff before a CSV download
Merge pull request #501 from technosailor/master

Add a hook to wpsc_purchase_log_csv() and make $headers3 an array
Remove debugging statement
Use strict comparison and fix whitespace issues

As per feedback from @JustinSainton.
Should now match http://make.wordpress.org/core/handbook/coding-standards/php/.
Merge pull request #493 from om4james/productmeta

Database Upgrade Routine to rename old _wpsc_* product metadata array
Filter $json_response object

Used quite nicely in conjunction with the new custom trigger.
Update Dutch translation
Merge pull request #511 from MPolleke/master

Updated Dutch Translation (partial)
Don't use wp_convert_bytes_to_hr() deprecated function. Fixes #508.

As per http://core.trac.wordpress.org/ticket/19067, WordPress 3.6 deprecates the wp_convert_bytes_to_hr() function in favour of the size_format() (which was was added in WordPress 2.3).
Merge pull request #512 from om4james/wp_convert_bytes_to_hr

Don't use wp_convert_bytes_to_hr() deprecated function
Add custom JS event for when cart is emptied

Necessary if you've, for example, hooked into the fancy notification event to update cart totals somewhere, and need to do the same when emptying the cart.