http://stackoverflow.com/questions/17406120/how-to-add-product-in-cart-programmatically-in-prestashop
https://www.prestashop.com/forums/topic/305190-adding-product-to-shopping-cart-from-a-custom-module-page/
https://www.prestashop.com/forums/topic/359896-prestashop-16-add-product-to-cart-programatically/
https://www.prestashop.com/forums/topic/332513-solvedhow-to-add-quantity-in-product-list-16/