Replace pseudo-private functions with file-scoped functions

Still working on #705, now going through [DynamicScene](https://github.com/AnalyticalGraphicsInc/cesium/tree/master/Source/DynamicScene). I'll add more commits soon.

Three tests fail but I was getting those failures with agi/master as well, I'm on Linux, so please run the tests on your end when you review. 

I'll report the errors on the forum.

Cheers.