* "keep layer name" will not try to modify layer names into
GDS layer/datatypes. The feature is available in the DXF
reader options and for the buddy scripts as "--keep-layer-names"
It applies to CIF too.
* "contour accuracy": when merging lines into contours, this
accuracy is applied to find neighbors. By default this value
is 0. If set to a value >0, points with distances (square
metrics) less than this value will be connected.
The buddy script option is --dxf-contour-accuracy=value.