Adding the IStoreInformationAboutEndpoints.OnEndpointDisconnecting event so that the ProtocolLayer can remove all the endpoint references. This
is not possible with only the OnEndpointDisconnected event because the ProtocolLayer needs the endpoint information which was removed before
the OnEndpointDisconnected event was send.

Also removed the OnEndpointConnected and OnEndpointDisconnected events from the ProtocolLayer because they are not necessary.