Added _deleted_conflicts to _view/conflicts.
Migrated reader.onload into function load_features.
Initialized feature array if properties are loaded with xml.
Added URL text input w/educational title.

I am well aware that Same-Origin Policy very much restricts the use of a URL
input field. Use cases are:
- Transfer selections in map.html between local DBs,
- attach selected documents to existing geometries,
- edit selected documents 'real quick' or something.
So, it's every time I stored ids and revisions temporarily, I wasted valuable
company time!!!
Added URL text input change hook.

Form logic is pretty much copied from $(":file").change(). Request errors are
displayed same place where parser errors go. File types are determined by the
response header, which is good enough for me. With Same-Origin policy I don't
expect any surprises there.
Fixed empty column glitch if fields query parameter is unset.