Hopefully finally sorted out the "http://www.xyz.cz?param" mess. The true

Hopefully finally sorted out the "http://www.xyz.cz?param" mess. The true
semantics turned out to be "http://www.xyz.cz/?param" and most web servers
really require "GET /?param".

I've changed the normalization rules to add the leading slash if needed
which also solves the relative URL problem I mentioned in the comments.

However, this means that the SEMANTICS OF NORMALIZED URL'S HAS CHANGED
and gatherer databases with URL's in the "http://www.xyz.cz?param" form
are now INVALID. I'm going to delete all such URL's from our gatherer now.