Don't make @unittest.DEBUG print the huge amount of verbosity generated by the synapse.storage loggers

Define a CLOS-like 'around' modifier as a decorator, to neaten up the 'orig_*' noise of wrapping the setUp()/tearDown() methods

Allow a TestCase to set a 'loglevel' attribute, which overrides the logging level while that testcase runs

Have all unit tests import from our own subclass of trial's unittest TestCase; set up logging in ONE PLACE ONLY

fix the copyright holder from matrix.org to OpenMarket Ltd, as matrix.org hasn't been incorporated in time for launch.