Implement a basic usage of Google Analytics

This fixes #82, but is just the first step
It took a couple of days for GA to start reporting, so
I'm not completely confident that we're getting enough info
yet, and there may have to be more app tracking added.

I gave GA access to @jstaffans and @jeanfrancoisbeaulieu for testing. 

This also makes some small changes to preference display, just removing the category.