[FIX] portal_sale: Move portal access rights to website_portal_sale

Currently as no portal backend view exists anymore, the method 'get_access_action' will return a url to the backend.

For example, if you have only sale installed (with portal_sale in auto install mode), you'll get access rights to sales orders in read mode in backend. The correct way to handle this is to return an access error and give the access rights to these documents only in website_portal_sale is installed, i.e. when the portal view is accessible in frontend under my/orders/ controller.