MEXICO CITY (Reuters) - At first, Mexico's government did its best to ignore Donald Trump. Then it likened him to Adolf Hitler. Now it has appointed a new ambassador to come up with a better plan. Fed up with the front-runner for the Republican presidential nomination labeling Mexico as a cradle of drug-runners, job poachers and rapists, the government is sending in respected diplomat Carlos Sada to lead a fightback. Mexico's new ambassador in Washington, Sada acknowledges his country has neglected its image across the border and aims to fix that with PR and media campaigns, and by lobbying prominent...