[dev] prefs of non-horde applications

[Chuck Hagenbuch]

Quoting dev at stean.ch:

> as far as I have seen that driver would be used by the whole
> Horde framework. However, I would need a special preferences
> backend only for one single registered application. The rest
> of horde should still use the default one. I have not yet
> found a clean way to tell horde that.

Best was is probably to use prefs hooks for that app, or a very  
hacked-up config/prefs.php file.

-chuck