[Simple-support] custom transformers

[Vladimir <kov...@ma...>]

I'd like to employ custom transformers for:

1. Field or property of type java.lang.Object
   (Framework is able to serialize the field as follows:
      <my-field class="java.lang.String">value of my-field</my-field>
   It raises TransformException when deserializing.)

2. Third-party clases with read-only access.