Of all of rock & roll's many comatose old tricks, few are hanging as tenuously to their life-support systems as that absolute relic known as the live album. Having said that, Rage's first such effort, From the Cradle to the Stage, benefits from a better premise (celebrating the enduring power thrashers' 20th anniversary), a better track listing, and a better overall recording quality than most half-hearted, contract-fulfilling entries into the format…