John Hopewell Chief International CorrespondentLetterbox Filmproduktion, producer of ZDF-Arte hit “Bad Banks” – and part of the Studio Hamburg Production Group that backed Netflix’s “Unorthodox” – has boarded “Davos,” a high-end drama series from Zurich-based film producer Content Film, producer of “Wonderland.”“Davos,” a period espionage thriller, is being written by Germany’s Julia Penner, head writer on seasons 3, 4 and 5 of “Druck,” Germany’s adaptation of “Skam,” and Switzerland’s Adrian