[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...
Is for entry points (same reason as above).
You just need to create a function, then setuptools will create an executable file which launch this function. In this case is ```main``` in all shinken/bin/*.py files