In order to provide a consistent user experience, we must sign the
user out from the main website if the community site provides a logout
button - else that button will appear not to work...
This system relies on http redirects and signing in to the main website
instead of using cross-internet pgsql connections and signing in individually
to each website.
This increases session security, obviously... It will also break local development
installs, which will have to add the two rows that this patch adds to the
documentation.
