TODO - Map quality

Boundary clipping

lakes missing from small_seattle
- just connecting the ends of ways doesnt always work well
- maybe increase the Bounds for areas, and let clipping clean up later?
some border intersections have weird OOBish geometry, or the arrows look weird
simplify border node detection, only do it in convert_osm?

bad polyline shifting remains
- from the remaining cases, looks like we need to totally remove some tight points and retry
- make polygons use the corrections too?
- bad polyline shifting causes jagged lane endings in generalized_trim_back
handle small roads again somehow?
- reduce degenerate min trim. the disabled fix doesn't look great.
- I40, I25, I0 cut corners when merged. disabled fix works, but breaks other things.
- try it bigger
- deal with loop roads?
- model U-turns
degenerate-2's should only have one crosswalk
- then make them thinner
car turns often clip sidewalk corners now
figure out what to do about yellow center lines
- intersections on one-ways look weird
- yellow and white lines intersect cars and turn icons and such
- who should own drawing them?
arrows
- sometimes head is separated from body. I314 montlake ped turn arrows

if building front path intersects another building, then scrap that building.
- or wait, just require bldgs to be even closer to sidewalk first.
- need to do polygon vs polygon check!
- will need to speed it up with quadtree containing entire buildings. make sure these are easy to use.
can we make OSM buildings with holes?
- experiment with https://docs.rs/clipping/0.1.1/clipping/gh/struct.CPolygon.html and https://github.com/21re/rust-geo-booleanop