Applied and tweaked smart-import patch from Mij, merging with 1.16.

Applied and tweaked smart-import patch from Mij, merging with 1.16.
This adds --source-wiki-url parameter to importImages.php for a wiki
from which to fetch the original uploader and comment.
Useful when going from local uploads to a shared repository.

Original code at http://www.howtopedia.org/public/mw-smart-import.tbz

"I release it with the least restrictive license applicable,
considering the code is derivative work of the respective
maintenance scripts from the MW distribution.
Feel free to commit this or modifications of it to your repos."
http://lists.wikimedia.org/pipermail/mediawiki-l/2010-February/033230.html