WASHINGTON — The U.S. economy turned in the weakest performance in three years in the January-March quarter as consumers sharply slowed their spending. The result fell far short of President Donald Trump's ambitious growth targets and underscores the challenges of accelerating economic expansion.The gross domestic product, the total output of goods and services, grew by just 0.7 percent in the first quarter following a gain of 2.1 percent in the fourth quarter, the Commerce [...]