Don't know what this was supposed to explain.
Removed local 'id' from _view/geojson to reduce maintenance.
This allows line #%-comments in GeoJSON_clone.

I figured if documents link to 50+ geometries it could be nice to be able to
add a hint, because that would make these large lists more manageable.
Simplified _list/tabulate using type inference.
Merged two #upload change handlers into one.
Be more stringent about Content-type.
Moved feature purge into $('#upload').change().
Moved geometry purge into $('#upload').change().
Moved finalization into $('#upload').change().

That is, fetch existing documents, set-up form elements, relay_geometry(). It
needs to be a function because files as well as the url use callbacks, so it
can't just go to the bottom of $('#upload').change().