Add Universal Analytics (bug 1018934)

~~We need to add some ability to merge settings with settings provided via the page like we currently do in webpay. That can likely be done as a separate thing though.~~ See: #73
I don't think we need to disable analytical "tracking" here. The DNT spec's definition: "Tracking is the collection of data regarding a particular user's activity across multiple distinct contexts and the retention, use, or sharing of data derived from that activity outside the context in which it occurred. A context is a set of resources that are controlled by the same party or jointly controlled by a set of parties." http://www.w3.org/TR/tracking-dnt/#dfn-tracking

That's not what we're doing by logging client side events for analytics and debugging.