SPOILER ALERT: This article contains details of tonight's series finale of Freeform’s Pretty Little Liars. UPDATED with after-show comments Showrunner I. Marlene King says she’s known for a couple years where Pretty Little Liars was headed, at least with regard to the identity of the mysterious A.D. And at least one cast member knew: Troian Bellisario said during the one-hour PLL aftershow on Freeform tonight that she asked King for the solution two years ago. Bellisario…