LOS ANGELES ??? Michael Feinstein knows that Love Is Here to Stay is an enchanting song with a sad story, its lyrics a tribute from Ira Gershwin to his brother and musical partner, George, who died at age 38.it is the sort of tidbit that Feinstein tosses off as deftly as he performs the tunes of the Gershwins, Irving Berlin, Cole Porter and other composers whose work collectively is known as the