Add 'Nature' genre

There is an increasing number of nature shows being produced and there needs to be a category distinct from Documentary to narrow them down.

Animal and environmental series would classify as being in both the Documentary and Nature genres... Similar to how a doc about a historical figure would also classify as Biography.

There are also scientifically-based narrative titles set in the world of nature. Animated shows like "Puffin Rock" don't fall under the umbrella of documentary, but they do classify as educating children about nature. This new genre suggestion would help nature fans find titles they wouldn't discover otherwise.