Don't query the database directly to get product custom meta
Instead get the post meta, and filter out unwanted values.

Note that the meta_id and post_id are no longer in the meta values array elements.
Use 'is_protected_meta'
added 'wpsc-product' as the meta_type
Merge pull request #1603 from JeffPyeBrook/pr-1602-remove-direct-query-to-get-meta

Don't query the database directly to get product custom meta