增加JSON格式解析支持（已附上代码），修复UnicodeDecodeError，增加默认sql_type

[mysqldba-nandy]

1. MySQL 5.7新增JSON格式，虽然没有MongoDB支持得那么好，但是用起来已经很方便了。烦请有时间新增对JSON格式的解析支持，谢谢啦~

   想了想，自己动手先实现一下，还请参考：

   import json
   ...
   def process_binlog(self):
   ...
   elif is_dml_event(binlog_event) and event_type(binlog_event) in self.sql_type:
       for row in binlog_event.rows:
           # add self.json
           if self.json:
               for column in binlog_event.columns:
                   # json(column.type) = 245
                   if column.type == 245:
                       value = row['values'][column.name]
                       if isinstance(value, dict):
                           value = json.dumps({fix_object(k): fix_object(v) for k, v in value.items()}, ensure_ascii=False)
                       elif isinstance(value, list):
                           value = json.dumps([fix_object(k) for k in value], ensure_ascii=False)
                       row['values'][column.name] = value
   
           sql = concat_sql_from_binlog_event(cursor=cursor, binlog_event=binlog_event, no_pk=self.no_pk,
                                               row=row, flashback=self.flashback, e_start_pos=e_start_pos)

2. UnicodeDecodeError: 'utf8' codec can't decode byte ... block = platform.system() == 'Windows' and block.decode("gbk") or block.decode("utf-8") https://github.com/danfengcao/binlog2sql/issues/33#issuecomment-449703838，这个`bug`也麻烦修复一下~

3. 感觉设置默认sql_type更加方便新手调试 self.sql_type = [t.upper() for t in sql_type] if sql_type else ['INSERT', 'UPDATE', 'DELETE']

[zj5220924]

1. MySQL 5.7新增JSON格式，虽然没有MongoDB支持得那么好，但是用起来已经很方便了。烦请有时间新增对JSON格式的解析支持，谢谢啦~ 想了想，自己动手先实现一下，还请参考：

import json
...
def process_binlog(self):
    ...
    elif is_dml_event(binlog_event) and event_type(binlog_event) in self.sql_type:
        for row in binlog_event.rows:
            # add self.json
            if self.json:
                for column in binlog_event.columns:
                    # json(column.type) = 245
                    if column.type == 245:
                        value = row['values'][column.name]
                        if isinstance(value, dict):
                            value = json.dumps({fix_object(k): fix_object(v) for k, v in value.items()}, ensure_ascii=False)
                        elif isinstance(value, list):
                            value = json.dumps([fix_object(k) for k in value], ensure_ascii=False)
                        row['values'][column.name] = value

            sql = concat_sql_from_binlog_event(cursor=cursor, binlog_event=binlog_event, no_pk=self.no_pk,
                                                row=row, flashback=self.flashback, e_start_pos=e_start_pos)

1. UnicodeDecodeError: 'utf8' codec can't decode byte ... block = platform.system() == 'Windows' and block.decode("gbk") or block.decode("utf-8") https://github.com/danfengcao/binlog2sql/issues/33#issuecomment-449703838，这个bug也麻烦修复一下~
2. 感觉设置默认sql_type更加方便新手调试 self.sql_type = [t.upper() for t in sql_type] if sql_type else ['INSERT', 'UPDATE', 'DELETE']

通过import json来处理，带来的一个问题是json中的元素顺序会发生变化