Checkbox for use of seasonal taps 3 and 4

SBZ has requested to add an additional checkbox to the [event create form](https://alex.ia.utwente.nl/scheduling/event/create/), which they would be able to see for the drinks.

The checkboxes should indicate if the organizer wants to use the 3rd and 4th taps (craft beer seasonal taps) during the drink. The reasoning is that in the MBasement those taps regularly go unused, so SBZ only wants to prepare kegs in the cooler if the taps are going to be used. If there are no drinks using the seasonal taps, the partial kegs can be moved to Abscint to be used there, instead of going bad.

The checkboxes should also be visible on the event details, for foundation managers and for the organizing association. They should also be editable on the edit event page so they can be updated.