Fixed bad geometry update logic.

The update logic now looks (or should look) like this:

* feature.properties.GeoJSON_clone updates doc.GeoJSON_clone, only if stated
  explicitly. That means it must be set as a field in the uploaded either an
  _id or null/""/etc.
* doc.GeoJSON will be updated if feature.geometry is set and doc.GeoJSON_clone
  is unset. This provides for all kinds of use-cases (see below).
* any doc.GeoJSON_clone identical to doc._id is removed from the document.

Use cases include but are not limited to:
- Change Fields Via XML:
  Just download with _rev, _id, type in new values, then upload again. New
  columns are added as new fields, columns with an empty header are ignored,
  empty cells remove an existing field.
- Change Fields Via GeoJSON: Download with _rev, _id AND geometry id. This
  tells the application that the geometry shouldn't be updated from
  feature.geometry.
- Attach New Documents To Existing Geometries:
  Download with geometry id and without _rev, _id. Define new and remove
  existing fields, upload again.
- Change geometry of existing documents:
  Download as GeoJSON, set GeoJSON_clone to null (in case the previous document
  was linking to an existing geometry rather than its own). Draw new geometry
  in QGIS, upload again.
- Delete Documents (this is my favourite!!!):
  Download, add a new column '_deleted'=TRUE(), upload.
Fixed missing opening bracket.
Transformed nested objects into flat columns.

Those are more useful outside any js environment, although they look silly (and
are useless) in JSON. Example:
{ Nutzung: {
    Jagdpacht: 3.5,
    Waldpacht: 0.2,
  },
  Fläche: 4.0,
  Gemarkung: "Bad-Gottleuba",
  Besitzer: ["LSH", "Andre Neumann", {Vorname: "Mike", Nachnahme: "Schulz", Wohnort: "Oelsen"}],
  "GrundbuchNr.": ["32b-12", "32b-15"] }
will flattened to
{ "Nutzung.Jagdpacht": 3.5,
  "Nutzung.Waldpacht": 0.2,
  "Fläche": 4,
  "Gemarkung": "Bad-Gottleuba",
  "Besitzer.0": "LSH",
  "Besitzer.1": "Andre Neumann",
  "Besitzer.2.Vorname": "Mike",
  "Besitzer.2.Nachnahme": "Schulz",
  "Besitzer.2.Wohnort": "Oelsen",
  "'GrundbuchNr.'.0": "32b-12", // fields with dots receive extra quotes
  "'GrundbuchNr.'.1": "32b-15" }
No changes in the logic, just minor clean-up.
Referenced wrong object 'properties' in upload.html.
Switched to db/_all_docs instead of multiple $.getJSON's.

The browser stalls a little if there are more than 500 docs.