Lines-class.Rdclass for sets of line objects
Objects can be created by calls to the function Line
Lines:Object of class "list", containing elements
	of class Line-class
ID:"character" vector of length one, with unique identifier string
signature(obj = "Line"): retrieve coordinates
	from lines; returns list with matrices
signature(x = "Line"): add lines to a plot
Lines-class, SpatialLines-class