Track pages when navigating back

[defagos]

Tracking pages when navigating is better for Mediapulse. We asked David from the GD measurement team if it was a problem that we do the same for Webtrekk as well:

No this is not a problem for me at all. The opposite is true: I favor any solution, where we have the same, unified behavior for any Endpoint (Webtrekk, ComScore, Net-Metrix) alike.

So we should now do it :)

[defagos]

Implemented a first iteration on feature/back-tracking.

I kept the displayed once boolean since it is used to inhibit page views in containers before they are first displayed. Not sure we should remove it, but this requires further testing.

Note that the rule for automatic tracking does not change. Tracking occurs on view appearance which depends on the kind of modal presentation.