duplicate settings for display of hatching area

[Klumbumbus]

With r14388 a check box to the view menu was added to disable the hatching. I just noticed the we already had this option at wiki:/Help/Preferences/Display#OSMData under the label "Draw boundaries of downloaded areas".
Both settings kind of conflict with each other, i.e. if it is disabled in the preferences, the check in the view menu has no effect at all on the mapview.

I think both settings should be unified.