RoomVC: Make membership events use less screen

Use MXKRoomBubbleCellDataStoring.tag to identify membership cells

Riot/Model/Room/RoomBubbleCellData.m

@@ -33,6 +33,12 @@ static NSAttributedString *readReceiptVerticalWhitespace = nil;
     
     if (self)
     {
+        if (event.eventType == MXEventTypeRoomMember)
+        {
+            // Membership events have their own cell type
+            self.tag = RoomBubbleCellDataTagMembership;
+        }
+
         // Increase maximum number of components
         self.maxComponentCount = 20;
         
@@ -441,4 +447,16 @@ static NSAttributedString *readReceiptVerticalWhitespace = nil;
     return readReceiptVerticalWhitespace;
 }
 
+
+- (BOOL)addEvent:(MXEvent*)event andRoomState:(MXRoomState*)roomState
+{
+    if (self.tag == RoomBubbleCellDataTagMembership || event.eventType == MXEventTypeRoomMember)
+    {
+        // One single bubble per membership event
+        return NO;
+    }
+
+    return [super addEvent:event andRoomState:roomState];
+}
+
 @end