Eliminate Undefined variable errors in wpsc_obtain_the_description

This poorly-written function is now less poorly-written. Removed
unneeded globals, test $_GET variables before using, removed direct
query to database
Typo in last commit

Got too carried away
Stop testing for category ID - just return output if set

Poor logic begets poor logic
Remove pubdate from product feed. Fixes #354
improve column widths on product page
improve featured star rendering.
improve product CSV import admin panel layout and behaviour. add support for more weight units. show up to 5 rows of sample data. feedback how many records were imported. support adding newly created products to no category.
improve product categories
bring more code up to coding standards
improve general admin tab layout
improve checkout fields editor to show heading hierarchy better
improve checkout settings. improve checkout form fields column widths. improve positioning of edit options link for select, check and radio boxes.
improve layout of tax settings admin page. bring files up to coding standards.
improve layout of fields in tax rates and tax bands.
basic layout improvements, but javascript is broken in this commit.
massively improved taxes settings forms in wpec admin panel.
Fix HTTPS product image links.
Make ajaxurl relative.  This is how it has been in WP Admin since 3.4.0.  Fixes #403
Add 'wpsc_vargrp_name' filter to allow customised display of variation group names.
When filtering the product list by category in the admin only show products in the selected category, not any of it's sub-categories.