TODO - Map quality

Boundary clipping

lakes missing from small_seattle
roads
- what if they start/end in bounds, but briefly dip out? arboretum place east
intersections
- some intersections partly cross border, is that actually fine?
use real map background by default

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?

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