INT-2845: Gradle: check XSD-versions in the tests

In many cases our IDEs import into test configs Namespace-resources
with hardcoded versions of Spring & Spring Integration XSDs.

It may produce build issues on different Spring versions.

And it exactly causes an issue during the transition to the new Spring Integration version (e.g. 3.0).

* Add Gradle task 'checkTestConfigs' to check test configs for hardcoded resources' versions.
* Add to 'test' task dependency on new task 'checkTestConfigs'
* Fix hadrcoded versions in the test configs.

JIRA: https://jira.springsource.org/browse/INT-2845