Make ga-tracked links respond to meta-click

Now if you cmd/ctrl-click on an edit pencil, it'll open in a new window; View Source Files can now also be clicked in a dev environment (previously that did nothing).

@nickpell 
Not sure if it matters, but this could benefit from gaTrackLink. Would have to do a little inversion. Going to leave as-is for now since I don't have much of a local environment to test this