The geometry selection form now behaves somewhat plausible.

If an existing geometry was selected to replace the new one, the new one won't
appear anymore in the form. Still very abhorrent!!! OH THE HUMANITY!!!
Exchanged 'doc' for 'feature' as member of the features array.

Also I checked for the presence of 'shape' in a more detailed way, so that js
doesn't throw exceptions anymore.
Unfortunately I don't see any way to provide the (WGS84-transformed) new
geometry after the documents have been uploaded WITH the GeoJSON_clone-member.
This means the user cannot revert-back the decision and the geometry stays
cloned. I could cache the shapes but meh....(There is probably no need to fix
this as long as noone complains. I see this as a minor problem.)