Introduces a new method of invoking tar. For backup the tar output is piped to
to openssl and then to dd which actually writes the file to disk. For restore this
procedure is reversed. Two new scripts are added to remove the encryption key from
the initrd, thus preventing it to be stored on the same media than the encrypted backup.
And a script for the initrd which prevents the restore process if no key is present.
At the moment there is no interactive user input for the encryption key, it has to
be entered in /etc/rear/local.conf before starting rear recover.