Improved documentation for setStorageCookieDomain

Documentation on using setStorageCookieDomain during local testing was not present. 

For local testing (i.e on localhost), the cookie domain should be set to an empty string. Setting the domain to 'localhost' will not work on all browsers since some browsers only allow you to set domain cookies for registry controlled domains, i.e. something ending in .com or so, but not IPs **or intranet hostnames** like localhost.