PRAVEEN MENON A white supremacist who killed 51 people at two mosques in New Zealand last year watched without emotion on Monday as relatives of his victims recounted the horror of a massacre which prosecutors said he carefully planned to cause maximum carnage. Australian national Brenton Tarrant, 29, has pleaded guilty to 51 murders, 40 attempted murders and one charge of committing a terrorist act during the shooting rampage in the city of Christchurch which he live-streamed on Facebook. He could be the first person in New Zealand to receive a term of life in prison without parole, when a…