Commits building up to the refactored UI

This pull request consists of a series of commits that build up to the fully refactored version of AppRTC as at [apprtc-m.appspot.com](https://apprtc-m.appspot.com).

The first commit is a minimal version of the new UI without any of the following: 
· analytics
· header/icons
· camera change
· sharing (except link)

Each subsequent commit will add these features.

I think at some point I had a problem with localStream not evaluating as true or false (can't remember exactly) so used the !! idiom. 

I've just tried out removing the !! here and elsewhere – seems to work fine.