Remove pointless #imports from .m and .h files

This was done with a brute-force approach, ensuring no additional
warnings from GCC 4.9 under x86_64.

UI/Scheduler/UIxCalMulticolumnDayView.m

@@ -20,17 +20,13 @@
  * Boston, MA 02111-1307, USA.
  */
 
-#import <Foundation/NSArray.h>
 #import <Foundation/NSDictionary.h>
-#import <Foundation/NSEnumerator.h>
-#import <Foundation/NSString.h>
 #import <Foundation/NSValue.h>
 
 #import <NGExtensions/NSCalendarDate+misc.h>
 
 #import <SOGo/SOGoUser.h>
 #import <SOGo/SOGoUserDefaults.h>
-#import <SOGo/SOGoDateFormatter.h>
 
 #import "UIxCalMulticolumnDayView.h"