Websocket implementation doesn't support unsubscribe for notifications

Current websocket mechanism has support for subscription for notifications but doesn't support unsubscribe for notifications.
This is required in re-connection scenarios for example if there is a socket disconnection due to any reason.
Current behavior of websocket implementation is that on the first connect of the websocket client, all the events present up to that point are sent as a create operation notifications. Subsequent re-connections do not result in notifications for those events. This will cause losing of events during the time of disconnection.
To insure no event lose client should be able to "unsubscribe" for notifications and then re-subscribe and in that case all the events will be received again.