Dashed line contours

From a user voice request.

Create the ability to change the type of line (e.g. dashed for negative) when creating contour lines

I’m trying to create contour plots for fields that range from negative to positive values, but I’m unable to easily change the negative one to dashed lines so they can easily be identified.

Dev note: This would as simple as letting lines render as dashed lines (similar to the line size option)