Isochrones

Goal

Implement a proper isochrone builder.

We adapt the current implementation with a proper polygon building algorithm like CONREC.

The main TODO's are:

[ ] Implement CONREC or use/port one of the existing implementations when open-source.
- Produce a LocalGeo.Polygon object from a set of points.
[ ] Find a way to adjust the current implementation without breaking it.

Planned