Live at Reading (2 Lp's)Certain concerts create a legend as soon as the final note ceases to ring. Nirvana's headlining appearance at the 1992 Reading Festival is one of these shows, a concert that arrived at precisely the right moment and stands as testament to a band at the peak of its powers and right before things started to turn sour within the Nirvana camp. Despite the happy news of the birth of Frances Bean Cobain a mere 12 days before this August 30 festival, rumors