added recipe for double tap to drag with drag lock

This PR adds a recipe to enable double-tap dragging along with the "Drag Lock" feature. This makes it easier to drag and drop windows/files/etc. with the trackpad.

![screenshot 2014-12-28 16 56 51](https://cloud.githubusercontent.com/assets/1480677/5565082/8ffe56bc-8eb2-11e4-9a75-612874a46fca.png)