Should artist-endowed foundations get into the authentication business? The black art renaissance, now and then, via Clifford Owens in New York, “Now Dig This!” in Los Angeles, plus David Hammons and extra. The Smithsonian’s National Portrait Gallery will get extra warmth from last year’s Wojnarowicz censor. Plus, video game art in D.C., and making sense of the Chinese public Art News sale growth. In Christie’s New York “Old Master Paintings” sale, Jan. 25, 2012, the NGA wins out over fierce competitors to amass its first painting by Dutch grasp Thomas de Keyser. ARTNET NEWSA judge fires the executor of the …