MOSCOW, March 19 (Reuters) - French adventurer Nicolas Vanier drove his team of dogs on to Moscow's Red Square on Sunday at the end of an 8,000-km (5,000-mile) odyssey through the world's biggest country. He said the hardest part was not the freezing Siberian wilderness, but early spring weather in the last few days, which melted the snow and forced him to fit wheels to his sled to reach Moscow. Vanier's journey, from Lake Baikal in eastern Siberia to Moscow, was the equivalent of travelling just under a quarter of the distance around the globe. It took place in temperatures...