Apprtc index.html updates

This is the second in a series of pull requests to enable transition to a 'mobile friendly' UI, along with some additional code tweaks. (See [apprtc-m.appspot.com](http://apprtc-m.appspot.com) for 'full fat' version.)

This pull request only has code formatting changes to apprtc/index.html: this version of index.html will work with other existing code.