Add support for parted flags to partitions

This is based on top op #26, so that one needs to merged in first.
I don't get this one. This implies `$?` will always be 0.  You couls as well do

```perl
$self->set_flags();
sleep(SLEEPTIME);
return 0;
```

or do you mean

```perl
if ($?) {
    $this_app->error("Failed to create $self->{devname}");
} else {
    $self->set_flags();
}
sleep(SLEEPTIME);
return $?
```
?