New report that writes a JUnit XML file 

Hi
I added a new report that writes a JUnit XML file. This report can be read by Jenkins. Like this the JS tests will show up like any other passing/failing JUnit test on the build server.

I'm aware that this is a big pull request. In order to get to the raw test results I refactored the connection between the PhantomTestRunner and the qunit-phantom-runner.js file.

Basically I did the following changes:
- qunit-phantom-runner.js no longer writes anything to the console. It just returns one big JSON structure.
- PhantomTestRunner converts the JSON to a Java model.
- PlainReporter uses the Java model for creating the file report.
- JsTestRunnerTask uses the Java model for creating the console output.

Any chance that this change gets integrated in to the main branch?

Cheers
michael