Thwart the bots

[brianpipa]

I added in better robots.txt and it looks like that helped.

Now it looks like there are multiple scrapers grabbing the KUBrowser data. Let's see if we can do something to thwart them a bit.

[brianpipa]

added bot-thwarting code in 4.1.0

[brianpipa]

Fixed this for real now, using a "captcha" in v.4.2.0