search for bus stops when double splitting a way

[Polyglot]

After the user selects 2 nodes, look for bus stops on either side of the resulting middle way (using expanding rectangles, or using the functionality used for sorting the stops according to the ways sequence, or the validation rule that determines that stops aren't served).

It should then become possible to predict that the user wants to add a bus_bay, and when also taking into account on which side the cars drive, whether it should be a right or a left bus_bay.