Set the has_js cookie for authenticated users

[deviantintegral]

This is a port of the merge request from Launchpad: https://code.launchpad.net/~andrewberry/pressflow/529252-has-js-cookie/+merge/69900

[pwolanin]

here's a simpler variant for just the has_js part:
https://github.com/pwolanin/6/commit/c59dd7705165050f44b4dd020beb16aac6f64583

[elliotttf]

This looks pretty good to me. Is there a reason you put the JavaScript in the header and not the footer? Even though what you're doing is super light weight it's generally better practice to put JS that doesn't need to run for the page to work in the footer.

[elliotttf]

And actually I think I like @pwolanin's approach a little better, it is definitely simpler. That won't blow up though if JS is disabled, will it?

[pwolanin]

In mine it's in the footer - that seems to work fine for batch+js. We have that in production.

[elliotttf]

I've moved this to another pull request (#29) that's closer to what @pwolanin implemented. Closing this one.