Cable definition

[rlescanne]

Cables are geometries that link ports to eachother. A port, is an oriented point in space with several properties (dedicated to define the geometry of the transmission line). We can put any number of ports in a draw_cable instruction since the definition is
def draw_cable(self, *ports, ...)
The port orientation is expected to be given in the following way (an example with 4 ports):

where the last one is oriented so that it "closes" the path.
This is quite inconvenient and should be modified such that all ports need to be defined in the same direction :