This is pretty hackish as fixtures can't be used during test discovery.
To properly shut down the driver I've added a conftest.py file that will
be called when quitting pytest. We might be able to handle this a
little better if we wrote a full plugin, but for now this works.
Also now reports all test indexes, so you can select e.g test 2 of a
tool.
We don't rely on TwillTestCase anymore, that is now exclusively used by
ShedTwillTestCase. Then I've just re-used the infrastructure of
ToolsTestCase for discovering tests, while making sure that we do use an
admin API key during testing.
mvdbeek