webperimental: Do not allow holes in known techs tree

Signed-off-by: Marko Lindqvist <cazfi74@gmail.com>
webperimental: Document differences to default web-ruleset

Signed-off-by: Marko Lindqvist <cazfi74@gmail.com>
Build threaded AI module

Signed-off-by: Marko Lindqvist <cazfi74@gmail.com>