W15B-a

1. add ReplyView and use it to manage and draw messages
2. implement asynchronous message sending function (draw message box in
chat room while waiting for sync, then draw the datetime right after the
message be written into the database)
3. remove unnecessary codes
4. avoid using #message and #msgbtn in chatroomView


1. 新增ReplyView來管理及畫出個別對話訊息
2. 實作非同步訊息上傳功能(發送訊息的同時先在本地端畫出對話，等訊息寫進資料庫後再根據回傳資訊畫出時間)
3. 移除不必要的程式碼
4. 在chatroomView中取消使用 #message 及 #msgbtn