Enough people uses LibreCAD for CAM work's and requires that the entities
that make a path are ordered so that the starting point of an entity is the endpoint
of the previous entity.
a very fast sorting of lines and arcs to the end point of an object is the starting
point of the following are using "draw->polyline->create polyline from existing sements".
With this command (only present in 2 series) the lines and arcs that have common
points becomes in a polyline, then just decompose it so that the lines are ordered