Underground set a record as WGN’s highest performing original series ever in its launch last night. The 10 PM airing drew 1.4M total viewers to rank No. 5 among all scripted series premieres on cable this broadcast TV season. The premiere’s  585K  adults 25-54 ranks No. 7 in the TV season that started last September. Across its four Wednesday night plays, the launch cumed 2.5M viewers, to stand as the best total-viewer opening ever for an original on WGN in same day viewing. The drama, created by Misha Green and Joe Pokaski, outpaced premieres of the network’sOutsiders by 27% and Salem by 6%.  Across those four plays, Underground delivered 983K…