A new setting "prefixQueriesWithStatementId" for XML configuration

Hi mybatis team,

I implemented a new setting "prefixQueriesWithStatementId" for XML configuration and would like to ask you to take a look and say your opinion.

This setting solves a problem which our team faced. We use mybatis in many applications, and all these apps have one more thing in common - they work with the same database. When you see the slow query log, it's not so easy to find out what application sent an unefficient query. This is the problem. I suggest adding a special comment to quaries as a solution, and using statement id can help us.

Here is an example of mybatis-config.xml with the new feature
```xml
<configuration>
    <settings>
        <setting name="prefixQueriesWithStatementId" value="true"/>
    </settings>
</configuration>
```

And if we have the following mapper configuration
```xml
<mapper namespace="org.apache.ibatis.submitted.prefix_queries_with_statement_id.XmlBasedMapper">
	<select id="getUserUsingParameterMarker" resultType="org.apache.ibatis.submitted.prefix_queries_with_statement_id.User">
		select * from users where id = #{id}
	</select>
</mapper>
```

the query will be
```sql
/* org.apache.ibatis.submitted.prefix_queries_with_statement_id.XmlBasedMapper.getUserUsingParameterMarker */
select * from users where id = ?
``` 

Please, let me know what do you think.

--
Best wishes,
Vlad.