test_cv_subscribe_system

Lets have another round and hopefuly prevent another bazzillion comments :-) :

1) if you thing that test_cv_subscribe_system attempts to test too much at once and I should first port the old promote/publish api tests before this one, tell me as well.

But I'd like to have this thing merged and then to move on to the rest of content-view stuff :-)
Again, bad docstring. Do not remove the whitespace after the summary line, read up on the relevant [Sphinx directives](http://sphinx-doc.org/domains.html#the-python-domain), and I advise adding trailing whitespace.