Club announcements

[JasonGrace2282]

Supersedes #1647

[shrysjain]

Copying over the to-do list

• [x] Archive club announcements
• [ ] Search club announcements
• [ ] Restrict subscriptions for restricted activities to only those on the authorized list
• [ ] Force club sponsors to be subscribed to announcements
• [ ] Rewrite intranet/apps/eighth/views/activities.py, lines 60-64 and intranet/templates/eighth/take_attendance.html, line 500 to allow both the eighth activity sponsors and the club announcements sponsors to edit settings
• [ ] Apparently add tests along the way (unfortunate)
• [x] Remove the homecoming banner from the club announcements page
• [x] For this text on the request post page: "Want to post an announcement for your club's members? Submit a club announcement instead!" add it for club sponsors as well (currently only for club officers)
• [x] intranet/templates/dashboard/dashboard.html show the announcement banner to everyone (not just officers/sponsors)

[JasonGrace2282]

There's currently a bug where club announcements for non-subscribed users are not showing... I'm working on it now. EDIT: Fixed

Otherwise, @shrysjain, I finished the "archive view" (which is just a show all button). If you have any feedback on it just lmk.