Display identical nodes only once in compact list in planner

[vmarc]

Suggestion from @pyrog:

One "logical" node sometimes consists of multiple "physical" guideposts on the ground. These guideposts have for example a distance of 10 or 20 meters between them, but they represent the same "logical" node.

Currently, in the route planner compact node list, all "physical" nodes are shown. It would be useful to show the "logical" node only once. For example, nodes in the same relation could be displayed only once, or nodes with the same name with a distance shorter than a given threshold could be merged into one node.