Add GeoJSON support for viewing files

Maybe with http://leafletjs.com/examples/geojson.html

Also see https://help.github.com/articles/mapping-geojson-files-on-github/

If we can accept a merge request depends on the dependencies this does or does not introduce.

/cc @JobV @dzaporozhets

Availability and Testing

Exploratory testing in the MR. Frontend specs to cover new functionality.