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.
I thought about this and decided that the code is simple enough to keep it all here, rather than referencing adapter.js. That means this (and the gum example) are completely self-contained.