Setup environment script

Hi all,

I added a script that setups a virtual environment for the ToolBox. It creates a virtually environment and installs the package on an editable mode. When the script is standalone and is not a member of the ToolBox package (e.g., copy pasted on a desktop), it downloads the repository.

This aims to facilitate the ToolBox setup, especially setting up for each proposal.

I uploaded the script at /gpfs/exfel/exp/SCS/201901/p002212/usr/Software/setup_environment.py, and one can run it with python setup_environment.py

@lleguy @mercadil @mercurio