AKSubmission: Respect Activation status

If an event is not active prohibit changes to AKs through frontend (at least?) such as AK Creation

changed milestone to %KIF 48,0

added feature high-priority work-in-progress labels

mentioned in merge request !25 (merged)

closed via merge request !25 (merged)

mentioned in commit 0d7f7870

mentioned in commit b1de3d45