Mark the outputPerTestCase flag of JUnitXmlReport as incubating.
Tabs to spaces.
GRADLEREV-11 - mention Test implements Reporting in release notes.

Also some minor tweaks to DSL ref/Javadoc in this area.
Improve assertions on JUnit XML output to test that no system-out type elements are present when not using test case output association.
Remove redundant reflective call.
Use UncheckedException.throwAsUncheckedException() and unpack InvocationTargetExceptions.