Allow specifying columnPrefix in constructor mapping.

[harawata]

It's used with resultMap (see the attached test).

<resultMap id="authorRM" type="Author">
  <id property="id" column="id" />
  <result property="name" column="name" />
</resultMap>

<resultMap id="articleRM" type="Article">
  <constructor>
    <idArg column="id" javaType="int" />
    <arg column="name" javaType="string" />
    <arg resultMap="authorRM" columnPrefix="author_" javaType="Author" />
    <arg resultMap="authorRM" columnPrefix="coauthor_" javaType="Author" />
  </constructor>
</resultMap>

This should fix #968 .

@kazuki43zoo , @h3adache ,
Please let me know if there is any concern.

[kazuki43zoo]

@harawata I think it's good.
But I have one question. Is not need adding columnPrefix attribute on @Arg annotation ?

[harawata]

Damn...you noticed! XD
I'll update the PR.

[kazuki43zoo]

👍

[harawata]

Thank you, @kazuki43zoo !

[h3adache]

Thanks @harawata! this is really useful!