FancyTracker-FF per Erik Zettergren

This is a modern adaptation of the original postMessage-tracker by Frans Rosén. The base logic and functionality still exists (at least it should work the same), although it has been built upon quite a lot.

A LOT of vibing has been going on in here, especially for this port over to Firefox due to repeated requests of the original chrome version over at https://github.com/Zeetaz/FancyTracker.