Hi Pascal,

You can make your own custom module to manage reset the cart by following below steps...

Step 1. Inherit template of cart and make one .xml file.

<template id="clear_cart_button" inherit_id="website_sale.cart" customize_show="True" name="Clear Cart Button">
  <xpath expr="//a[@href='/shop/checkout']" position="before">
    <a href="" id="clear_cart_button" class="btn btn-default mb32">&lt;span class="fa fa-trash-o"/> Clear Cart&lt;/a>  
  </xpath>
</template>
<!-- This template is use to add .js file inside webiste. -->
<template id="assets_frontend" inherit_id="website.assets_frontend" name="Shop">
 <xpath expr="." position="inside">
    <script type="text/javascript" src="/website_sale_clear_cart/static/src/js/website_sale_clear_cart.js"></script>  
 </xpath>
</template>

Step 2. Make .js file inside /startic/src/js folder to make click event of the link.

$(document).ready(function () {
$('.oe_website_sale').each(function () {
    var oe_website_sale = this;
    $(oe_website_sale).on("click", ".oe_cart #clear_cart_button", function () {
        openerp.jsonRpc("/shop/clear_cart", "call", {}).then(function(){
            location.reload();
        });
        return false;
    });
});
}); 

Step 3. Add controller inside .py file to manage request of clear cart.

class pos_website_sale(http.Controller):
    @http.route(['/shop/clear_cart'], type='json', auth="public", website=True)
    def clear_cart(self):
        order = request.website.sale_get_order()
        if order:
            for line in order.website_order_line:
                line.unlink()

That's it. It will add one functionality inside cart template for clear/remove all products from the selected cart.

I am sure that it is very useful for you.

Free App is out at Odoo Apps Store now. You can download  and use it.

Odoo Technical notes is published for this. You can view Technical Stpes to reset a shopping cart in Odoo 8 Website  and review it.