Web-based wiki editing improvements

Good news, everyone!

I've added CSS properties, adjusted some JavaScript code, and done some
pixel art to style the wiki's login and editing pages.  Web-based
authentication and editing of the wiki should be usable now.

The editing help page [1] has been updated to reflect these

Also, there's a small minimally intrusive challenge–response anti-spam
measure on registration now.  We haven't had any issues with spam, but
I'd like to keep it that way.

Please let me know if you encounter any problems.

Of course, the wiki is still also editable by anonymous Git.

[1]: http://www.proteanos.com/wiki/editing/

Patrick "P. J." McDermott