ISPConfig Vacation support

Basically, the support consists of two classes, one derived from Ingo_Script and another one derived from Ingo_Transport.  Also, ingo/config/backends.php is modified with an example config.

I'd be happy to get some feedback.  Can I leave the extensive debugging code in the code?  Is there framework support for debug messages which should be used?

ISPConfig doesn't support a user configurable vacation reason.  So I would like to hide the corresponding form field in the Ingo webinterface (or make it readonly).  What is the best way to accomplish this?  I'm thinking about modifying Ingo_Form_Vacation::__construct(), handing over an additional parameter with the list of form fields to hide.