Convert SVG bezier traces to KiCad curves

[JarrettR]

With KiCad 8, arbitrary shapes can be connected to nets. Instead of the Inkscape hack with adding line segments to approximate curved traces, this can now be done natively.

The s-expression for the curves are like this:

	(gr_curve
		(pts
			(xy 66.4748 93.278) (xy 62.7248 90.378) (xy 64.2748 96.428) (xy 61.012077 95.482793)
		)
		(stroke
			(width 0.2)
			(type default)
		)
		(layer "F.Cu")
		(net 7)
	)

That ends up looking like this:

The four sets of points will end up looking like this in Inkscape: