How do we categorize Uncle Vanya, Anton Chekhov's play about family life on an estate and working farm in late nineteenth century rural Russia? Is it a comedy, a melodrama, an excursion into absurdism à la Samuel Beckett's Waiting for Godot? The answer is, it can be fitted into any or all of these, and playwright Heidi Schreck's appealingly accessible adaptation at Lincoln Center's Vivian Beaumont Theatre generous…