Switching from relay_geometry(feature) to relay_geometries().

I can't really foresee what's happening if I spawn a bunch of these functions
in parallel. There's a small probability that everything will work as intended
and there's the feasible outcome that the staged FeatureCollection contains
wrong _id's, duplicate features etc.
Migrating to relay_geometries().

Most of this stuff (including comments) is copied from relay_geometry and
covers what must be done before GeoJSON clones are ready to be fixed:
- For each feature that provided geometry, check if it is staged to either get
  a GeoJSON_clone or for deletion,
- query _view/geojson-doc to get all potentially affected document ids,
- query _all_docs for documents missing from uploaded_docs and features.
Hashed document feature[f].properties._id to feature[f].
Spliced rows that reference the document to itself.

Because documents may also contain geometry but nothing else (this happens when
the type attribute is unset), I can't just prevent _view/geojson-doc to emit
those.
This also prevents the HTTP-get if no documents are affected.
A crappy draft of what has been in the previous function.

It is the same logic, but restricted to rows that have the same key:
- Check if we have a document that the old geometry can be safely stored into,
- otherwhise just remove the type attribute, and
- successively replace GeoJSON clones where needed.
Absorbed a couple of off-by-one indexes into r.
STASHED WIP FOR NEXT WEEK:

- added GeoJSON_clone to #modify div
- unstaged unchanged features from upload
- set default title attribute in map.html