Bug 1069915 - Privacy Panel

This is a new pull regrets for the Privacy Panel. I am very sorry to open another pull request instead of reopening the old one, but before I thought twice I have deleted my mold branch and had to reopen everything from the beginning. 
One more question, this item should be hidden by default and use the mozSettings key to show it if we enable this feature on developer panel. You can check my latest comment on bugzilla for this part.