added link to the seller name in product_detail.php . On clicking it, the user is taken to another page "seller.php" where he see all the products listed by this seller only. Here also provided the option of search by keyword  or category as in the index.php . Added new functions to product.php to include seller id in WHERE clause
Merge pull request #17 from ramyaps/master

Additional functionality : Search products listed by a particular seller