http://jpfoss.blogspot.com/2012/04/distance-between-point-and-line.html
distance d, point P, line from point A to B
http://www.chegg.com/homework-help/questions-and-answers/find-distance-point-p-1-4-3-line-l-x-2-t-y-1-t-z-3t-using-following-methods--l-line-2-spac-q1450324