QtIFW

Doc: update docs for Modify Extract Installer example

Fix issues in the example files and unify some values to
make it possible to use standard text for the configuring
section.

Change-Id: I4e4236d519d075fc1f0461e3b863989ca0373cd3
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>