WASHINGTON (Reuters) - The chairman and board of directors of a group that has pushed for an end to the U.S. embargo on Cuba announced their resignations on Wednesday to protest executions and jailings on the communist-run island. "The regime's sudden, wholesale repression of human rights is incomprehensible as a matter of policy, and unacceptable as a matter of principle," leaders of the nonprofit Cuba Policy Foundation said in a statement. In the last month, Cuba has imprisoned 75 dissidents for terms of up to 28 years in a move to stamp out pro-democratic opposition to Cuban President Fidel Castro's...