jshint: js code validation and beautification

As discussed with Justin, this pull request includes the following changes: 

1. Ran JavaScript beautifier, as per jsbeautifier.org – this is not strictly anything to do with JSHint but makes it easier to spot invalid code. (We may want to tweak code layout further at some point – opinions vary...)

2. Added global 'use strict' to main.js and updated code to avoid errors.

3. Added JSHint options to main.js and updated code to validate.

@juberti and @marwahvikas PTAL.

Done.


On Sun, Jun 8, 2014 at 10:52 PM, Justin Uberti <notifications@github.com>
wrote:

> In samples/web/content/apprtc/js/main.js:
>
> >    pc.createOffer(setLocalAndSendMessage,
> > -                 onCreateSessionDescriptionError, constraints);
> > +    onCreateSessionDescriptionError, constraints);
>
> indent 4 here
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/GoogleChrome/webrtc/pull/71/files#r13526449>.
>