Currently sessions set on (www.openfoodnetwork.xxx) are not usable on the bare domain (openfoonetwork.xxx). When transitioning from one to the other, the user's session is completely lost.
This change means sessions on subdomains (including www) will be transferable.
The cookie store is not big enough in some cases. In order to solve a
CookieOverflow error and maybe track down the underlying issue this
patch uses the database instead of cookies to store session data.
