Fix replace maintenance tool binary.

Missing QInstaller::init() did lead to crashes cause of
uninitialized lib7z (in case we used a zipped file as input).
In verbose mode console did not show up. Get rid of KDSaveFile
as it complicated to code unnecessary.

Change-Id: I5911c895d7763e4ce919b1d4761568e47b244b1b
Reviewed-by: Kai Koehne <kai.koehne@digia.com>