You've seen them, walking with purpose through crowded concourses, waiting alertly at curbs, at special events--in every walk of life. Sometimes you glimpse them on the news, in areas that have been struck by natural disasters (building collapses, avalanches, earthquakes, mudslides) or touched by war--first responders who are put into some of the most dangerous and challenging missions on the planet. They are service dogs and working canines, or "Good...