Ch 1499 - respect "do not track"

The changes to the qunit tests here have nothing to do with this story because (I ended up not being able to write a test for this - see comment in tests subtask) - they are just a simplification that I want to sneak in here :)
IE 9 is down to mini numbers (thank, god) but apparently uses a different prefix: https://developer.mozilla.org/en-US/docs/Web/API/navigator.doNotTrack
I can't remember if we're current - 1 or current - 2 (I should know this).