Repeat curve styles

This is useful if several curves are plotted and you want the colors to repeat.

If the wrap index is e.g. set to 4 and 8 curves are plotted, the first 4 curves will get colors as selected from the Default Curve Styles list. But the 5^th curve will get the same color as the first curve; the 6^th curve will get the same color as the second curve, etc.