[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...
Can't we can avoid this? modules dir was not need in 1.4 vesion, so if we can have no such entry in the test conf, it will also test migrated 1.4 versions :)