Add simple cgi based web interface

Based on current Foris one, just made it work locally without Foris. Not meant to last, meant to be rewritten, but should help us till we get the time to do some deeper rewrites.

Do not review thoroughly the web part. It is meant to be replaced and the goal is to preserve status quo while dropping Foris and not to waste time on review of web page that will be rewritten.

With this, we can create a separate package, put Pakon into webapps and drop Foris in 6.0.