- removed legacy adding of metaboxes on admin_footer

The metaboxes are already called on the register post type callback.
This is entirely redundant.
New functions to trigger error in case of deprecated function, file,
argument or doing it wrong

_wpsc_deprecated_function()
_wpsc_deprecated_file()
_wpsc_deprecated_argument()
_wpsc_doing_it_wrong()
Properly deprecate functions that we previously did wrong.
Fix documentation.
Fix: JavaScript error in variations.js
Fix: Product category pages don't respect pagination and sort order
settings.

This is only reproducible if a navigation menu is registered to the
primary nav menu area but doesn't have any menu item.

The bug is introduced after this commit in WP core:
https://github.com/WordPress/WordPress/commit/a269ba85f77cb9c8c67fe623d2ff2501aca498ba

Issue #128 and issue #134.
Make sure product category page respect pagination and product order settings.  Props garyc40.
Re-generate products pages' IDs after plugin reactivation.

Issue #132.
- adding hook to clean up what gets hooked on
  wpsc_purchlogitem_links_start

See Github issue
https://github.com/wp-e-commerce/WP-e-Commerce/issues/122

Basically just making a proper spot for developers to hook in to when
they want to add non-link metaboxes.
Fix: PHP Warnings when bulk editing variations.

This only happens when bulk editing newly created variations for a
new product (before it is saved to the database with all the product
meta).

Issue #75.
Return cart item messages as key => value array rather than HTML.
The needed filters for compatibility between WPML plugin.
The needed filters for compatibility between WPML plugin.
Adds necessary filters for WPML integration on Checkout Field names and Variations.  Props dominykasgel, garyc40, JustinSainton
Fix: Manual / Test Payment instructions don't appear on transaction
results page and email.

Issue #95.
Fix: Switching a purchase log status to "Closed Order" doesn't
reduce stocks.

Pull request for #89