Donald Trump has been accused of being “the most corrupt president in history” after commuting the prison sentence of a friend and former adviser.Roger Stone was due to begin a 40-month prison term in Georgia, US, on Tuesday after being convicted of lying to Congress,obstruction and witness tampering.Trump stepped in to spare jail but not pardon Stone after a court denied a request to delay the start of the term.Democratic senator Elizabeth Warren said the move showed Trump was the most