Chat screen: Timestamp and message edition display.

We unify here the design across iOS and Android:
- The messages is over the full width.
- The time stamp is at the user name level.
- If several messages are sent in a row, clicking on a message (not the first one) will make it move slightly down to display the timestamp just above.
- On the right side of the timestamp we would have an "Edit" icon.

Vector/Model/Room/RoomBubbleCellData.h

@@ -24,8 +24,6 @@
 /**
  A Boolean value that determines whether this bubble contains the current last message.
  Used to keep displaying the timestamp of the last message.
-
- CAUTION: This property is presently set during bubble rendering in order to be used during bubble cell life.
  */
 @property(nonatomic) BOOL containsLastMessage;
 
@@ -34,4 +32,19 @@
  */
 @property(nonatomic) BOOL hasReadReceipts;
 
+/**
+ The event id of the current selected event inside the bubble. Default is nil.
+ */
+@property(nonatomic) NSString *selectedEventId;
+
+/**
+ The index of the most recent component (component with timestamp). NSNotFound by default.
+ */
+@property(nonatomic, readonly) NSInteger mostRecentComponentIndex;
+
+/**
+ The index of the current selected component. NSNotFound by default.
+ */
+@property(nonatomic, readonly) NSInteger selectedComponentIndex;
+
 @end