UC-18 Add Tracking for Facebook interactions

We need a way to independently track user Facebook interactions (login, connect, disconnect, logout...)
This PR adds those tracking code, so that we can track these actions internally and on GA.

RFCR @garthwebb & @lizlux 

Ticket: https://wikia-inc.atlassian.net/browse/UC-18
looks like login and register's attributes of rel=nofollow were already set in line 26.