* Put module-info.class into Multi-Release JAR folder
Uses ModiTect to place module-info.class under Multi-Release JAR folder
`META-INF/versions/9`.
* Adjust pom.xml to drop support for Java 6
* Change doclint setting
All Javadoc errors have been solved previously; doclint can now be enabled
without causing build failures.
* Improve README Java requirements
In this test, we are registering a tree type adapter for Id but it never gets invoked. Instead, the reflective type adapter gets invoked causing an exception.