[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...
In fact, ```python setup.py install``` or ```python setup.py develop``` will create those files.
Look in setup.cfg in entry_points section