It’s the closest thing yet to an ABBA reunion: computerized avatars of Sweden’s legendary disco group will perform during a televised tribute to the quartet to be broadcast this autumn, ABBA member Bjorn Ulvaeus said Thursday. Agnetha Faltskog, Anni-Frid Lyngstad, Bjorn Ulvaeus and Benny Andersson split up in 1982 after dominating the disco scene for more…