Separate product types created by hook_commerce_product_info from those created though the interface.

Right now there are no apparent changes from products which are created through the interface and stored in the database, and those you can define with the hook_commerce_product_info. This can lead to some puzzled administrators, since you are allowed to both edit and delete these product types, but when you try to do so, nothing happens as they are still defined in the module. These options should be disallowed, or the links to them should at the very least be removed.