NEW Introduce cost price on product.

htdocs/core/class/html.form.class.php

htdocs/core/lib/product.lib.php

htdocs/fourn/class/fournisseur.product.class.php

htdocs/install/mysql/migration/3.8.0-3.9.0.sql

htdocs/install/mysql/tables/llx_product.sql

...cs/install/mysql/tables/llx_product_fournisseur_price.sql

htdocs/langs/en_US/products.lang

htdocs/product/class/product.class.php

htdocs/product/fournisseurs.php

htdocs/user/card.php