Revert most of 227a60a4.

The help engines findFile() does already resolve virtual folders in
different namespaces, so the added code was superfluous. It did not
even work properly... Implement a redirect network reply, so when a
file from e.g. qtwidget is linked into qtcore, we will get the valid
url set inside the address bar. This also fixes "Bookmark" handling,
"Sync to Contents" as well as "Copy" and "Hover" actions.

Change-Id: I418af5962d9f1d9970febb07f8f1c52e9995c58c
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>