Add a preferences window

This adds a preference window with default preferences to change the
sparkle options and to set a custom path to a git binary.

PBNSURLPathUserDefaultsTransfomer.h

@@ -0,0 +1,16 @@
+//
+//  PBNSURLPathUserDefaultsTransfomer.h
+//  GitX
+//
+//  Created by Christian Jacobsen on 28/09/2008.
+//  Copyright 2008 __MyCompanyName__. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+
+@interface PBNSURLPathUserDefaultsTransfomer : NSValueTransformer {
+
+}
+
+@end