Jim Carter, the British actor better known to most of you as Mr. Carson, the butler on the PBS period drama “Downton Abbey,’’ was at the Somerville Theatre Friday to host a fund-raiser for victims of last year’s devastating earthquakes in Nepal. The evening featured stories and magic — ventriloquist Lesley Smith was the emcee, after all — and a talk by humanitarian aid worker Linda Cruse, who updated the audience on the recovery efforts in Nepal.