Multiple organisers per event

One-sentence description

Multiple organisers per event

Motivation

I noticed that since the introduction of the Partnercie (once again) multiple committees (and the board) involved in events increased (Lunches are board + partnercie, laser tag was evc + partnercie). It would be quite useful if an event can have multiple organisers. With the new societies this might happen even more often, think 'EVC + board game society'.

Desired functionality

Select more than one organiser per event.

Food for thought

• Currently you can only select the groups you belong to as organiser unless you're a board member. That's not useful if you want to add a group as organiser that you're not in
• The organiser determines the mailing list that is used for the unregister notifications. Should all organisers have a mailing list to enable that option? Do we send all organisers that email?