Privacy Panel new pull request

This is a new pull request. We had to remove the old one due to big problems with git and some Schroedinger patches....
I got a question here, will PP app be installed from market place or not ? If yes, please follow https://github.com/mozilla-b2g/gaia/blob/bf1a629614c9454117e96002284cd0878b4c94ac/apps/settings/js/panels/root/themes_item.js#L58 to make sure we will automatically update the visibility. (To be honest, you can directly reference all `themes_item.js` and this can speed up the review process if you don't know what to update)