OSIS-1856 Moved common aggregate to manager
OSIS-1856 Moved common aggregate to manager

	modified:   base/models/education_group_year.py

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