Removed parseInt() in favor of implicit type conversion.
Included XML parser in upload.html (work in progress).

Here's a condensed version of the progress so far:
- File type is fetched from file name extension,
- provided useful error messages for unknown extensions, parser errors,
  wrong/insufficient data,
- parsed opening/closing/singleton XML tags into one handy multidimensional
  array 'tables',
- matched tag attributes and stored result as element[attrib]=value,
- normalized 'ss:Index'ed columns,
- mapped 'ss:Type' attribute to JSON type.
I still need to acknowlege _rev, _id, GeoJSON_clone. These will be used to
either update existing documents or create new documents from existing
geometries.
Reduced amount of rows processed by _list/export.

If key compression is used for large datasets, _list/export might end up
skipping a lot of keys at the beginning. Unfortunately we don't have a
skipRow() function to bypass JSON.parse of exhaustive geometry objects, wink,
wink.
I worked around the offset by providing start_key and end_key. And because I
don't want to end up sorting index lists twice, I modified lib/indexes to
remember if they have been sorted before. Hooray for dynamic objects.