Get Facebook integrated into uProxy

Get Facebook integrated into uProxy: https://github.com/uProxy/uproxy/issues/409

This is the first draft of Facebook in uProxy, which I am submitting so people can play around with it, and so we can make incremental improvements using this as a benchmark to compare to (in terms of functionality, spam, etc).

There are many known issues with uProxy in Facebook, but we will try to fix as many as possible in the facebook social provider (freedom-social-facebook), rather than in the uProxy codebase.  Hopefully we won't have to make any changes for Facebook in uProxy/uProxy after this pull request.....

Known issues (most of these are expected to be fixed in freedom-social-facebook):
* Lots of "spam" notifications
* Can't detect when peers go from online to offline
* Log out, then log in again doesn't work right (shows all friends as offline)
* Login notification shows meaningless ID number, not name
* No account chooser shown when you login to Facebook, and if you are already logged into Facebook on that Chrome Profile and have given OAuth Permissions, it launches and then immediately closes a new tab (looks weird and can result on you focusing on the most far-right tab, which may not be where you were focused before clicking login)
* Doesn't show non-uProxy FB contacts, and has no way to invite them
* Not tested in Firefox (waiting on Firefox to be fixed for GTalk first, which is waiting on the upgrade to Freedom 0.6)

Tested login for Facebook and Google in Chrome, re-ran "grunt test"