Added functions to create a copy of the segment and update its references.
Added a function to clean any invalid reference.

Solved a bug: In the add_nodes() function: the width attribute is used instead og the get_width() function to get the actual width (not scaled by the scale_factor).

Completed the feature to copy the whole structure and update the references.

Road nodes from diferent roads at the same location are fused.
Road nodes can belong to multiple lanes: each has a vector of parent lanes and geometries.

Added support to link road segments.

TO DO: add the functions to link road segments.