oc: Honor calendar WebMail UI permissions on OpenChange library

By expanding roles from the given ACL to have these values as flags
inside the OpenChange library. This only applies to Calendar and
Tasks folders which stored four different access rights to three
different types of events/tasks.

As the events and tasks are stored in the same table, I have added
two new classes to manage permissions in the same way and this
avoids the code duplication called MAPIStoreCalTask(Folder|Message).

OpenChange/MAPIStoreAppointmentWrapper.m

@@ -1080,6 +1080,29 @@ static NSCharacterSet *hexCharacterSet = nil;
   return owner;
 }
 
+- (NSUInteger) sensitivity
+{
+  NSString *accessClass = nil;
+  NSUInteger v;
+
+  accessClass = [event accessClass];
+  if (accessClass)
+    {
+      if ([accessClass isEqualToString: @"X-PERSONAL"])
+        v = 0x1;
+      else if ([accessClass isEqualToString: @"PRIVATE"])
+        v = 0x2;
+      else if ([accessClass isEqualToString: @"CONFIDENTIAL"])
+        v = 0x3;
+      else
+        v = 0x0;  /* PUBLIC */
+    }
+  else
+      v = 0x0;  /* PUBLIC */
+
+  return v;
+}
+
 /* sender representing */
 - (enum mapistore_error) getPidTagSentRepresentingEmailAddress: (void **) data
                                                       inMemCtx: (TALLOC_CTX *) memCtx
@@ -1242,23 +1265,8 @@ static NSCharacterSet *hexCharacterSet = nil;
 {
   /* See [MS-OXCICAL] Section 2.1.3.11.20.4 */
   uint32_t v;
-  NSString *accessClass;
-
-  accessClass = [event accessClass];
-  if (accessClass)
-    {
-      if ([accessClass isEqualToString: @"X-PERSONAL"])
-        v = 0x1;
-      else if ([accessClass isEqualToString: @"PRIVATE"])
-        v = 0x2;
-      else if ([accessClass isEqualToString: @"CONFIDENTIAL"])
-        v = 0x3;
-      else
-        v = 0x0;  /* PUBLIC */
-    }
-  else
-      v = 0x0;  /* PUBLIC */
 
+  v = (uint32_t) [self sensitivity];
   *data = MAPILongValue (memCtx, v);
 
   return MAPISTORE_SUCCESS;