Those who prefer their accidental-murderer-with-a-guilty-conscience stories to be brooding and inconclusive will get a kick out of “Whitewash,” the more-or-less one-man dark comedy from Canada, starring Thomas Haden Church, and the small-scale Irish drama “What Richard Did,” both currently showing at the Tribeca Film Festival. Set in remote stretches of wintry Northern Quebec, Emanuel Hoss-