Retain node OSM data when reading multi-polygons
Besides not losing tags on such nodes, this also retains OSM ids in all cases now, which simplifies geometry reassembly considerably, as this gives us a lot fewer nodes to consider for merging.
Besides not losing tags on such nodes, this also retains OSM ids in all cases now, which simplifies geometry reassembly considerably, as this gives us a lot fewer nodes to consider for merging.