Packaging

[pbordron]

Update setup.py in order to target many install use cases

Until now, doing a pip install dgenies install dgenies ready for cluster (with web server dependencies and drmaa). We can target something like that:

• pip install dgenies -> dgenies standalone
• pip install dgenies[web] -> dgenies web (mysql driver is not installed)
• pip install dgenies[drmaa] -> dgenies web+drmaa
• pip install dgenies[node_scripts] -> only dgenies scripts needed for cluster nodes

Drop old python versions