[dev] Patch to ease navigation in prefs UI

[Chuck Hagenbuch]

Quoting Mathieu CLABAUT <mathieu.clabaut at free.fr>:

>   Attach is a small patch which allow people to navigate from a
>   preference group to the next or previous preference group, without
>   having to click on the "return to options" button.

Committed, thanks. I think I want to clean up the UI some, somehow, and get
the HTML out of PrefsUI and into a template, but it's a good feature. Thanks!

-chuck

--
Charles Hagenbuch, <chuck at horde.org>
must ... find ... acorns ... *thud*