In the world of Conor McPherson’s 1997 one-actor play, St. Nicholas, vampires are surprisingly ordinary, observes the unnamed Irish protagonist played by Kevin Webb in Ed Rutherford’s new staging at Black Button Eyes Productions. Sure, they may be obsessively compelled to count items such as grains of rice, but garlic and holy books aren’t such a big deal, aside from the risk of bad breath posed by the former.