Barring some unforeseen development, the last legal hurdle that might have prevented the District’s same-sex marriage law from going into effect was removed last week. D.C. Council member David Catania’s gay marriage countdown clock reads “2 Days!” as of this morning, and both the city government and the D.C. Superior Court have now released helpful instructions for couples looking to waste no time in getting their applications in. Here’s how it’ll work: Beginning at…