CDK-538: Added unit tests for DataModelUtil.
Merge pull request #146 from joey/datamodelutil_tests

CDK-538: Added unit tests for DataModelUtil.
Javadoc fixes.
Update release notes for 0.15.0 release.
[maven-release-plugin] prepare release release-0.15.0
[maven-release-plugin] prepare for next development iteration
Update jdiff files.