CAF::Render to render structured text

In `CAF::Process` because you may have passwords in the command line. In `CAF::File*` because, when showing the diff, there may be passwords in there, and those would end up in the logs.
Mmm... if this becomes a subclass of `CAF::FileWriter`, indeed there are circumstances in which you don't want the log.

You could encapsulate your `if ($self->{log})` into a function that does exactly that, say

```perl
sub do_log {
    my ($self, $method, @message) = @_;
    $self->{log}->$method->(@message) if $self->{log};
}

...
$self->do_log("verbose", "something");
```

I'd favour this approach (which we can even share with `FileWriter` and `Process`) better than this dummy logger.