Added @ExpectedQuery annotation to expose assertEqualsByQuery DBUnit feature

We are using spring-test-dbunit in our team's Integration test Suite. We have this need to compare the expected xml against a subset of data in the database table. DBUnit itself has an assertEqualsByQuery that allows you to do that. I added a new annotation @ExpectedQuery that would help us use this particular DBUnit feature using the annotation. I believe the broader spring-test-dbunit community would benefit from this feature. Please review my changes and suggest any recommendations.

Thanks
Sunitha