Show crop outlines on geosearch from nypl project

[timwaters]

This amazing site: http://spacetime.nypl.org/maps-by-decade/#/ allows browsing of maps from NYPL warper. it extracts the cropping masks into geojson, buffers and simplifies the resulting outlines. We can use this in the geosearch view, and potentially to also export it in the API

https://github.com/nypl-spacetime/group-maps see https://github.com/nypl-spacetime/group-maps/blob/master/index.js