Continuous improvement of powerline analyser

[flacombe]

It is proposed the following changes in osmosis_powerline analyser:

• Add ways with their nature and voltage as element result for classes 2, 4 and 6. Already supported for 5 and 7. It will allow to filter by voltage unfinished power lines and non power node on power line warnings.
• Rework of pseudo-graphe logic for class 8, with complete support of edge cases like https://www.openstreetmap.org/node/978980055 (two parallel osm ways on the same tower, currently leading to bogus https://osmose.openstreetmap.fr/fr/issue/7e56c73f-4332-28c1-9c5e-a2a6e1291adb)
• Fix False positive for "Connection between different voltages" #2494, now conflates not only osm voltages but their phase-to-ground equivalent (/ sqrt(3))

This work has been supported by Oh my grid initiative

Tests are still undergoing but comments are welcome

[flacombe]

We are all set for squash and merge @frodrigo

[frodrigo]

Lint code