[web/navigation] use add_onload instead of inline javascript href This way our javascript code isn't thrown out by the html cleaner e.g. when using the rql rest directive and a table view. To make things simpler, we now always use ajax URLs for navigation, even when we would previously have used regular links. Closes #3501626

../../doc/book usr/share/doc/cubicweb-documentation
../../doc/html usr/share/doc/cubicweb-documentation
../../debian/cubicweb-doc usr/share/doc-base/cubicweb-doc