oc: Implement edit own and delete own in GCSFolders

And returning back PidTagCreatorName.

This is done by checking the owner of the resource if the given
permission is restricted to edit/delete own items.

This requires a52bc3b to work in calendar folders as it requires to store and retrieve
the MAPI custom permissions in the ACL.

OpenChange/MAPIStoreGCSMessage.h

@@ -23,6 +23,8 @@
 #ifndef MAPISTOREGCSMESSAGE_H
 #define MAPISTOREGCSMESSAGE_H
 
+#import <SOGo/SOGoUser.h>
+
 #import "MAPIStoreMessage.h"
 
 @interface MAPIStoreGCSMessage : MAPIStoreMessage
@@ -30,6 +32,11 @@
 }
 
 /* subclass helpers */
+
+/* Return the message original creator */
+- (NSString *) creator;
+- (NSString *) owner;
+- (SOGoUser *) ownerUser;
 - (void) updateVersions;
 
 @end