Change do not track tests and page object region to suit the new numeric preference and UX
xfailed test_kill_app_from_cards_view due to
[Bug 915138 - Cards view can have a maximum of 3 cards](https://bugzilla.mozilla.org/show_bug.cgi?id=915138)
Merge pull request #1355 from AlinT/cards_view_fail

xfailed test_kill_app_from_cards_view due to
Merge pull request #1349 from zacc/change_do_not_track_prefs

Change do not track tests and page object region