Add new option to choose the stock status displayed on front when the product quantity greater than zero.

By default opencart works this way:

- if quantity is > 0: display "In stock"

- if quantity is 0 or lower: display the "Out of stock status" that have been selected for this product

Once module installed you have new possibility, if you let by default it will work as normal opencart but you can also select an "In stock status", so the result is like this:

- if quantity is > 0 and no custom status selected: display "In stock"

- if quantity is > 0 and custom status selected: display the selected in stock status

- if quantity is 0 or lower: display the "Out of stock status" that have been selected for this product