data-preparation: Crucial improvements to network_pt collection

[nihar1024]

### Tasks
- [ ] Filter Europe OSM .pbf to discard non highway entities (output .o5m)
- [ ] Use ST_ExteriorRing function to get correct perimeter geometry of sub regions (for .poly file)
- [ ] Clip Europe OSM to sub regions (but drop relations, author, etc), convert back to .pbf