Add Vector3 input

[pehrlich]

This show allow pinch and momentum-toss of a 3d textured object projected in to a 2d viewport normal to the camera. This would allow manipulation of 3d variables with the leap motion, in tools such as:

• http://www.lab4games.net/zz85/blog/2014/11/15/resizing-moving-snapping-windows-with-js-css/
• https://github.com/brianpeiris/RiftSketch
• http://threejs.org/editor

cc @GabrielHare

Edit: This is the 1-dimensional analog (repeated three times):

This is the 2-dimensional analog:

The three dimensional version will take some invention