[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...
Because this imply a name conflict in setuptools:
```import shinken``` could mean import ```shinken``` or ```shinken.bin.shinken``` when you are in shinken/bin folder.