Add anniversary as event type

[henrygraesberg]

No description provided.

[junlarsen]

Hm sure, but do you think adding another enum kind is the best solution - or what is the rationale for doing so?

[brage-andreas]

I think we removed the type from OW4 since we thought we could use social instead, since this will be used exactly once every five years

[junlarsen]

I think a better thing is to specialcase the organizing committee when the event is made by jubkom, similar to how we did for velkom