成员的完整列表，这些成员属于 NEMeetingMessageChannelService,包括所有继承而来的类成员

-	addMeetingMessageChannelListener:	NEMeetingMessageChannelService
-	clearUnreadCount:callback:	NEMeetingMessageChannelService
-	deleteAllSessionMessage:callback:	NEMeetingMessageChannelService
-	getSessionMessagesHistory:callback:	NEMeetingMessageChannelService
-	queryUnreadMessageList:callback:	NEMeetingMessageChannelService
-	removeMeetingMessageChannelListener:	NEMeetingMessageChannelService