[WIP] Rework setup.py (virtualenv-compatible)

Hello !
We have begun to rework the setup.py to be virtualenv compatible
Of course, this could/should be merge after the 2.2 release...

We are currently fixing tests, but most of it works...
maybe we can already add cherrypy3, it's strongly a good idea to run with it. basic swsgi mode got tcp close problems, and I think I'll deprecate it in a future release;