[OSIS-3357] Refactor styling of excel
[OSIS-3357] Refactor styling of excel

	modified:   base/business/education_groups/reporting.py

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