refactored code to get possibility to give LearningUnit or EducationGroup child instances
refactored code to get possibility to give LearningUnit or EducationGroup child instances

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