Helps #4277

ImageDraw operations chord, ellipse, pieslice and rectangle take optional arguments outline with a default of None and width with a default of 0.

At present, specifying an outline and a width of zero stills draws the outline. The following three lines all produce the same result -

draw.rectangle(BBOX2, fill="green", outline="yellow")
draw.rectangle(BBOX2, fill="green", outline="yellow", width=0)
draw.rectangle(BBOX2, fill="green", outline="yellow", width=1)

This PR changes the behaviour so that a zero width produces no outline. For backwards compatibility, it changes the width default to 1, so that these two lines still produce the same result -

draw.rectangle(BBOX2, fill="green", outline="yellow")
draw.rectangle(BBOX2, fill="green", outline="yellow", width=1)

but

draw.rectangle(BBOX2, fill="green", outline="yellow", width=0)

does not.