THERE IS A CERTAIN TYPE OF ROCK MANAGER whose clients become the means to express his own artistic vision: in the late Fifties, Larry Parnes groomed his stars and gave them names which were supposedly descriptive of their characters, such as Steele, Wilde, Gentle, Fury, Power, Eager; in the early Sixties Andrew Loog Oldham manufactured the Rolling Stone?? bad-boy image; and Pete Meaden discovered