By Elizabeth Piper, Andrew MacAskill and Muvija M LONDON (Reuters) – Liz Truss said on Thursday she was resigning as British prime minister just six weeks after she was appointed, brought down by an economic programme that sent shockwaves through financial markets last month and divided her Conservative Party. Speaking outside the door of her Number 10 Downing Street office, Truss accepted that she could not deliver the promises she made when she was running for Conservative leader, having lost the faith of her party. A leadership election will be completed within the next week to replace Trus…