By Sarah Mills LONDON (Reuters) – British boy band One Direction, one of the pop music industry’s biggest acts in the last two years, plan to show the world what they’re really like in a new 3D documentary which will premiere in London on Tuesday. The five singers told a news conference in the British capital on Monday that “This Is Us” allowed them to present themselves in a more fulsome manner than they are depicted on videos, in concert and on the ubiquitous social media sites which track their every movement on and off stage. …