Append suffix to cookie name
If I run two Redmine instances on the same server (connecting to different databases and using two TCP ports),
the "_session_id" and "autologin" cookies don't work correctly because they are shared between the
two Redmine instances.
If there was a configuration option (stored in the database) which defines a suffix that is appended to the cookie name,
different Redmine instances may have different cookie names. So the cookies won't get in each other's way.