WASHINGTON/REDWOOD CITY, California (Reuters) - Republican presidential candidate Mitt Romney opened a new front on Wednesday in his fight against President Barack Obama, accusing him of presiding over a failing U.S. education system in the grip of union bosses who refuse to accept reforms. In a rare diversion from his campaign focus on the weak economy, Romney laid out an education plan in a speech that represented his most overt appeal to date to Hispanic voters who have largely sided with the Democratic incumbent. ...