Bug 940647 - Move bookmark creation to operator variant app

In my opinion, this adds unneeded complexity to the configuration JSON.   
It would be better using just aData.bookmarks.forEach(function(bookmark) {
As it stands now, this line implies that the configuration json will have the form:
{
  browser: {
    bookmarks:[
      {
       -- bookmark 1 data---
      },
      ...
      {
       -- bookmark n data ---
      }
    ]
  }
}

But since this json will be exclusively for the browser, everything we're processing is browser related. And so, the first key can be implicit, and so we can use aData.bookmarks.forEach instead of aData.browser.bookmarks.forEach. This way:

 * Although every configuration file has it's own peculiarities, the more similar they are (representing similar information on a similar way), the easier the configuration and the automation are.
  * The data needed for bookmarks and topsites configuration are very similar. If the configuration JSON follows the same pattern:
{"key": [
  { --elem 1 --},
  { --elem n --}
]
}
  then the modifications needed for the build.js (which is used to create the build)  are very small, and most of the already done work can be reused.