GRID  Add a grid on a 2D plot
    
    Add the property/value pair 'grid','on' to add
    a grid on your plot, e.g.
    
    plot(x,y,'grid','on')
    
    The grid color is the default background color.
    To change the grid color the pair can be of the type
    
    'grid',[r g b]
    
    where each r,g,b value is in the interval [0,1].
    
