View all projects based on recent activity

[titlecharacter]

As a user looking for projects to join, or a staff member making sure that projects are active, it would be good to see projects sorted by recent activity. Activities could include:

• Check-ins at hack nights
• Written updates
• Code check-ins for github-hosted projects (see #73)

Basically, we can be generous for what counts as an 'update' but still rank by date of most recent activity.

[mariekers]

Only view projects in active stages - 'Hibernating' projects are still showing up in the list