Added admin screen for the pizza orders
Closes #89
Short description
Adds an admin screen for the pizza orders, such that the organising party can easily manage which pizzas are paid.
Steps to use this feature
- Open the pizza event.
- Press the 'Pizza' button.
- Press the settings cog in the app bar.
- Manage pizza orders in the same way that you can manage event registrations.
Edited by Gijs Hendriksen