Move landing page new notebook to the bottom

Nothing needs to change at this point if there is going to be much work. I just want to point out that,
Ideally the cell hierarchy should come from bkNotebookCellModelManager (bkSessionManager.getNotebookCellOp()), that is, the model (as in MVC). $scope.getNestedLevel (should have been deprecated) and $scope.getParentId() should have been refactored to the cell model manager instead of relying on the view logic.

Also, note although this works, this is finding getNestedLevel through the prototypal chain. As commented in the definition of getNestedLevel(), the parent is $scope.$parent.$parent (hasOwnProperty("getNestedLevel") === true).