Demo updates

I've now updated all the non-apprtc WebRTC demos:
- tweaked HTML, CSS and JavaScript to validate with HTMLHint, CSSLint and JSHint 
- updated remaining demos to the new UI (though haven't done this for the face and desktopcapture demos)
- fixed various other minor wording and code formatting glitches.

@juberti @andresusanopinto @marwahvikas PTAL – but check my email first.
It would be good to have some document that describes all this boilerplate for the benefit of new sample pages.