Set verbosity on paver test tasks

@clytwynec, can you take a look at this? It's a pull request into your pull request.
Actually, looking closer... it seems that verbosity is only used in test_system (meaning cms and lms) right now. 
I think you need to pass it through to PythonTestSuite (for it's default subsuites that are used here) and to LibTestSuite for the cmd for common/lib tests(like you already did for SystemTestSuite)