Chris Willman Music WriterAhmir “Questlove” Thompson has announced his second feature film as a director quickly on the heels of winning both the grand jury and audience prizes at Sundance this month for his first documentary, “Summer of Soul (…Or, When the Revolution Could Not Be Televised).” He’ll return to that same era and musical milieu with a a documentary about Sly Stone, the frontman of Sly and the Family Stone, a group that appeared in 1969 footage used in “Summer of Soul.”“It goes