Fix [-Wformat-security] warning.

Change-Id: Iae180cb0f13a39daacc1cadd04094bfddd33b6ab
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Split out the file IO stuff and adjust other files respectively.

Also adjust the API to use QFileDevice instead of QIODevice to
make clear we just operate on files here and not on any possible
device like sockets, processes etc...

Change-Id: I4ecbb6e244fe4bb666ed12e62f9f5586bc1347f0
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Don't use QObject::tr().

Change-Id: Icefbff9851a4e096a4b800adea7d17db756abe99
Reviewed-by: Kai Koehne <kai.koehne@digia.com>