Better display of geoJSON areas

[corviday]

When a watershed is selected, three geoJSON objects describing it are drawn on the map: the boundary of the watershed (provided by geoserver), the path from the watershed to the sea (provided by the downstream API), and the network of streams within the watershed (provided by the watershed-streams API).

Currently these objects are run through some fragile parsing code and then displayed by the SimpleGeoJSON PCIC code, copypasted from plan2adapt. I believe that the newer version of leaflet used in this package has provision for display geoJSON objects, and we don't need SimpleGeoJSON.

Do one of the following:

• use native Leaflet geoJSON display
• move SimpleGeoJSON to the pcic-react-components library so it can be updated from everywhere at once, and write more robust geojson parsing code

[corviday]

Also, possibly update pcic-react-components to the newest version, which would also involve updating react.

[corviday]

@rod-glover alerted me to the existence of jsts, which might also be useful for improving our geoJSON handling.