Germany's Greens have enshrined in their election programme plans to abolish the contested Nord Stream 2 pipeline to ship Russian gas to Europe's biggest economy, creating a hurdle to a potential alliance with the conservatives.Chancellor Angela Merkel's conservatives, who have backed the Nord Stream 2 pipeline opposed by the United States, are leading in polls ahead of September elections and are seen as most likely to seek a coalition with the ecologist Greens that are forecast to come second.Armin Laschet…