Police and soldiers are on alert in Paris ahead of Friday's Olympic opening ceremony, featuring a parade of about 10,000 athletes through the heart of the city aboard boats along a 6-kilometer route on the river Seine.Extra anti-terrorism measures have gone into effect as more than 300,000 people, including world leaders, are expected to watch the ceremony from the riverbanks.For the first time in Summer Olympics history, the opening ceremony will be held outside a stadium.The police imposed a security perimeter along the riverbanks on July 18, shutting the area off to anyone without a pass…READ FULL ARTICLE