code style: when trying to set debug output level via trace(), use a separate parameter
implements JOO-60
JOO-60 Improve logging of JooUnit tests in PhantomJS
http://jangaroo.myjetbrains.com/youtrack/issue/JOO-60

There is a new Maven flag <debugTests> (boolean) to add
#joo.debug to the test URL. This applies for PhantomJS as
well as Selenium.
The PhantomJS test runner now does a much better job in
logging. Uncaught exceptions are dumped with a full stack
trace. You can use trace("[INFO]", "some info"); in your test
code, and the Maven build will log this output with the
corresponding log level (ERROR, WARN, INFO, DEBUG).