First Hello Cupcake, and now Ben & Jerry’s joins the list of dessert purveyors helping D.C. gay couples celebrate their newly granted marriage freedoms. Keith Spangler and Andreas Vellios plan to exchange vows inside the Georgetown Ben & Jerry’s Scoop Shop on Thursday. Rev. Lance Orndorff will officiate the ceremony, but the couple will also be celebrating with the actual Jerry — Jerry Greenfield, the co-founder of Ben & Jerry’s — who plans to…