Description
 class for line objects Objects from the Class
Objects can be created by calls of the form new("Line", ...),
or (preferred) by calls to the function LineSlots
    coords:- Object of class 
"matrix", containing the
	line coordinates   
 Methods
    - coordinates
 signature(obj = "Line"): retrieve coordinates
	from line   - lines
 signature(x = "Line"): add lines to a plot