Compute distance between point given as (px, py) and line spanned by points (lx1, ly1) and (lx2, ly2). From http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
Compute distance between point given as (px, py) and line spanned by points (lx1, ly1) and (lx2, ly2). From http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html