FullScreen works on FireFox, Safari, Chrome

But we lose the UI controls and clock due to styling.
Condense browser-specific fullscreen methods
Fullscreen the wrapper, not just cesiumContainer, to get UI controls
Make header title more Jenny-like.
Toggle fullscreen works: Chrome, FireFox, probably Safari; IE???

Safari's hanging, beachballing for me and my fan's wailing, but this
used to work -- going full-screen. I can't test toggling out of
fullscreen though.

And I sure can't test IE-du-jour.