OSIS-4179 Add SITE_ID setting in base.py for the "sites framework"
OSIS-4179 Add SITE_ID setting in base.py for the "sites framework"

uclouvain/OSIS-Louvain,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis