RoomDataSource: Add a property to show or hide timestamp when selecting an event.

Riot/Modules/Room/DataSources/RoomDataSource.h

@@ -34,6 +34,11 @@
  */
 @property(nonatomic) BOOL markTimelineInitialEvent;
 
+/**
+ Tell whether timestamp should be displayed on event selection. Default is YES.
+ */
+@property(nonatomic) BOOL showBubbleDateTimeOnSelection;
+
 /**
  Check if there is an active jitsi widget in the room and return it.