Add looping to VideoPlayer

Although this works, I'm not sure this is the correct way to do it.

The VideoPlayer contains a  Video, both of which have an "eos" property as a boolean. The CoreVideo (in video/__init__.py) has "eos" as a string, which already works with a 'loop' value. All rather confusing. 

So this facilitates the setting of the CoreVideo "eos" for looping, but passed through two classes whose "eos" is a different type? Perhaps it would be better to add a "loop" boolean property to the CoreVideo so it's clearer?