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