INT-2845: Gradle: Check XSD Versions in Tests

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

This may produce build issues with different Spring versions.

It also causes an issue during the transition to a 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
Merge pull request #691 from artembilan/INT-2845