English correction
Update single-product.html

The append field is missing here, it cause a bug on the category view : you can't add twice the same product to the cart by clicking the "Add to cart" button. You can reproduce the bug on the Thelia demo here : http://demo.thelia.net/?view=category&locale=en_US&category_id=83, try to add twice the "Lexie" chair for instance.
Using typed comparison as null == '' is true
Usinf the "data" attribute to calculate the "checked" value
Merge pull request #960 from stephaniepinet/patch-1

English correction
Merge pull request #963 from roadster31/checkbox-fix

Module configuration parameter & checkbox form field fix.
Merge pull request #962 from xockduo/patch-1

Fix add to cart bug in single-product.html