Adds support to configure if the sale price and the 'Add to cart' button is shown on products in the shop or not.
This setting is configurable under Website > Configuration > Settings:
When this configuration option is checked on we change the following things for public (not logged in) users:
- Hide the sales price on the /shop overview page
- Hide the sales price on the /shop/product-xyz page
- Hide the 'Add to Cart' button on the /shop/product-xyz page and show a 'Login to see Price' button
