The new Kenneth Lonergan play has a name — “Medieval Play” — and a director: Lonergan himself.Show was announced in the fall and skedded for a May slot as part of the inaugural season at the new venue of Off Broadway’s Signature Theater. At the time, however, there were no title or plot details attached to the play. Storyline of “Medieval Play,” a comedy about two French knights in the late 14th century, reps something of a departure for Lonergan, who’s better known for contempo tales including “This is Our Youth,” “Lobby Hero” and 2000 pic “You Can Count on Me.” Scribe-helmer, whose most recent Gotham stage outing was “The Starry Messenger” in 2009, last year saw the delayed release of his film “Margaret,” toplined by Anna Paquin. Lonergan is one of a quintet of writers tapped by Signature to be part of its Residency Five program, a new-work initiative that will yield three preems each from Lonergan, Katori Hall (whose “Hurt Village” opens later this month), Will Eno (on tap for the upcoming “Title and Deed”), Annie Baker and Regina Taylor. “Medieval Play” begins perfs May 15 ahead of a June 7 opening. Further production details, including casting, remain to be announced.