AUI 1366 Keyboard Accessibility

Hi Marc,

I've changed the toggle feature so that, on the parentNode, a left arrow keypress collapses the list and a right arrow keypress expands it.

Further, I made it so that if you press left inside the list it returns to parentNode and if you press right it moves to the next parentNode. I'm not sure if you'll want to keep it, but it seems like a nice feature to add.