WSUG: Convert ``Advanced Topics'' to AsciiDoc.

Leave most of the content intact for now.

Change-Id: Ie91fda8a3fe6ea2eb4c47acf7c41d7e6979235b0
Reviewed-on: https://code.wireshark.org/review/3938
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Gerald Combs <gerald@wireshark.org>