增加了对BytesExtra的解析，基本达到图片视频微信能看本地就能看的程度。其他类型消息的BytesExtra也顺带解析了（一个道理，以后可以从这里扩展）

app/DataBase/msg.py

@@ -56,7 +56,7 @@ class Msg:
         if not self.open_flag:
             return None
         sql = '''
-            select localId,TalkerId,Type,SubType,IsSender,CreateTime,Status,StrContent,strftime('%Y-%m-%d %H:%M:%S',CreateTime,'unixepoch','localtime') as StrTime,MsgSvrID
+            select localId,TalkerId,Type,SubType,IsSender,CreateTime,Status,StrContent,strftime('%Y-%m-%d %H:%M:%S',CreateTime,'unixepoch','localtime') as StrTime,MsgSvrID,BytesExtra
             from MSG
             where StrTalker=?
             order by CreateTime