After the Washington City Paper acknowledged the Black Cat near the top of the pack in its 2008 best-of category for dance clubs — right up there with monosyllabic sweat-halls Town and Love — the Cat had a crisis of conscience. For some time now, most Friday and Saturday nights have been guaranteed to be themed dance nights with names like Mousetrap, Bliss, Homo/Sonic, Cryfest, and CATatonia. That means choice weekend slots not reserved…