iCloud sync fixes.

[REMOVED]   OS X: Disabled ability to add new sites from OS X until I
            have time to implement it properly without causing
            duplicates etc.
[MOVED]     iCloud and Core Data support was centralised to iOS and OS X
            to make sure both platforms always use the same container
            configuration.
[FIXED]     iCloud sync problems.
[REMOVED]   iCloud KV is not used/needed.

MasterPassword/Mac/MPAppDelegate.h

@@ -13,13 +13,6 @@
 
 @property (assign) IBOutlet NSWindow                                    *window;
 
-@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator    *persistentStoreCoordinator;
-@property (readonly, strong, nonatomic) NSManagedObjectModel            *managedObjectModel;
-@property (readonly, strong, nonatomic) NSManagedObjectContext          *managedObjectContext;
-
-+ (NSManagedObjectModel *)managedObjectModel;
-+ (NSManagedObjectContext *)managedObjectContext;
-
 - (IBAction)saveAction:(id)sender;
 
 - (void)loadKey;