Admin Sort by products_model

for osCommerce Online Merchant v2.2

This is a very minor contribution, but something that I find useful. Basically it allows you to see the product model numbers in the admin category/product listing, and also sorts by model number. I work on a site that sells women?s clothing, and has many products by different vendors that have very similar names. The changes in this contribution just saves me time while looking for a specific product to edit. This should work with most snapshots. I have tested it with one from mid August 2002, November 2002, and January 16, 2003.