remove stale IPs from session, so we don't show outdated information

could happen if there once was a IPv6 connection, but now is not any more.
it now kills infos older than 3 minutes from the session.

it also shows the age of the infos now on the hosts overview view (but not on home view due to cosmetic reasons).

optimization: only request the fake images for ipv4/v6 detection if we don't have a fresh IP already.

added example settings for using detectip on (ip6-)localhost