documentation broken: points to dead links and causes privacy breaches when packaged

The documentation/*-site-header.qdocconf and documentation/*-site-footer.qdocconf files reference dead URLs, badly search+replaced and probably not appropriate at all, as in the DEB package we build with these documentation files, cause privacy-breach warnings in lintian.

In official Debian package, the maintainer must assure (policy wise) that no URL in a web-like document points away from the local system.

Such URLs in Debian packages will be complained about with RC bugs, if people spot them.