Removed empty bracket pairs if time is unset.
Beautified MS-Excel time string on upload.

They look something like 2001-09-03T00:00:00.000 even if the time provides no
information at all. Also I reserved the dash for time ranges, of which
LibreOffice is not capable.
Lucklily there is Data -> Text to Columns that enables me to revert cell
content to plain text. Sometimes the menu item is disabled for no reason at
all, though.
This is a work-around for duplicate shapes in upload.html.

It is the best I can come up with at this late our. It fixes duplicate shapes
on the geometry selection map canvas that are left uncleaned if the user skips
to the next feauture. As far as I can guess, they are produced by the following
combination:
User updates docs and has GeoJSON_clone set explicitly to the document id (to
inform the application that no update of the Geometry is needed). He then
decides to check for similar geometry.
In this case I accidently queried for [GeoJSON_clone,0] and identically for
[feature.id,0] and stored my geometry twice in feature.items[GeoJSON_clone].
This is a cleaner solution to that last UI glitch.
Rephrased caption to something like 'Use Own/New Geometry.'

This also applies to document updates.