Cherry pick from cesarandreu - sortable hacks - https://github.com/cesarandreu/angular-dragon-drop/commit/4393052baad35a92955d5ba69282e2b676e5e6e1 / https://github.com/cesarandreu/angular-dragon-drop/commit/8b2a68b824506031f810f6e4235e62d492f1f88e