Update registration status on event cards if it has been changed

[davidkrantz]

If one enters an event via the event card on the home tab or introduction matrix and e.g. signs up for the event and then go back, the text on the event card has not been updated with the new registration status. This issue refers to implementing a way to update this registration status if it has been altered.

The function that sets the registration status, setRegistrationStatus defined in home.js, might be of use.