UKPrefsPanel, UKUpdateChecker and UKFeedbackProvider updated

I've tracked down a couple of leaks/missing strings in some of these Cocoa classes, and the fixed version is up at

http://www.zathras.de/programming/cocoa_stuff.php

as always. Note that UKUpdateChecker and UKFeedbackProvider are combined in the "NiftyFeatures" project.

UKPrefsPanel is a controller class that takes a Tab view and a couple of image files and adds a toolbar to the window which you can use to switch between them.

UKUpdateChecker implements the "Check for Updates..." menu item, plus automatic update-checking at startup in one intuitively usable and re-usable object.

UKFeedbackProvider implements a simple "Send feedback" menu item that either opens a web site for providing feedback, or brings up mail with a message addressed to the developer and containing a meaningful subject line.