Add the option to output the results of a single failed test

[bleskes]

At the moment, the showOutput onerror (default) option causes the output of an entire test suite to be outputted when a single test fails. This is fine but sometime the test output is very verbose, or a suite contains many tests. In this cases it's beneficial to have the output of the single failed test as opposed to have to filter the suite output to zoom onto a single test. Ideally this will controllable using an annotation on the class level.