Make registration deadline, cancellation deadline, and number of registrations...

Ghost User
2020-01-25T17:45:09+01:00

Closes #919

#### Previous behaviour
Steps to reproduce:

1. View an event with a registration deadline, cancellation deadline, and a number of registrations on thalia.nu without logging in.
2. You can see the registration deadline, cancellation deadline, and the number of registrations.

#### New behaviour
Steps to validate that it works:

1. View an event with a registration deadline, cancellation deadline, and a number of registrations on thalia.nu without logging in.
2. You cannot see the registration deadline, cancellation deadline, and the number of registrations.