Add the incognito mode on TV in the settings

changed milestone to %3.6.x

added Android TV label

requested review from @Skantes

Nitpick, but I think it would be better to disable the "Persistent incognito" setting when incognito is disabled on TV.

The description of "Persisent incognito mode" is "Keep the incognito mode enabled even if the app is restarted" why might be confusing to some users with as it is enabled by default while "Incognito mode" just above is disabled.

Apart from that LGTM