[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...
Why rename to .py ? If it's not required I prefer to keep them untag, it's more cleaner. Users don't care it's written in python or another thing :)