front-page announcements

Thom Wiggers
2017-12-10T21:12:33+01:00

Allow to place messages on the front page in much the same way the current announcement ribbon works.

### Desired behaviour

1. Add an announcement text with visibility dates to the admin.
2. Within the date window, display the message on the front page.

### Use cases

1. In-memoriam announcements
2. Special event announcements, such as lustrum or intro.