AUI-1614 Add keyboard accessibility to drag and drop

Hi @jonmak08,

https://issues.liferay.com/browse/AUI-1614

Here is a preliminary implementation for the keyboard drag and drop. Right now, this will work for draggable components that does not use the dd-delegate. Mike and Drew are working on the dd-delegate, but I want to try to get this pushed in first so we can add more stuff to it and to make sure we are heading the right direction. Please let me know if you have any questions. Thank you!