Betty Davis was different — three-javelins/thigh-high-silver-boots/skyscraper-Afro/Egyptian-warrior-from-outer-space-getup-on-her-album-cover different. And a whole lot more besides. For decades, Davis’s uniqueness was known only to rare-funk specialists and assiduous beat-diggers. But now, thanks to Seattle-based Light in the Attic Records, her eponymous 1973 debut LP and 1974’s They Say I’m Different are available to…