/stats/: Global stats about schoolsyst itself

[gwennlbh]

• Number of registered users
• Number of active users (logged in in the last 2 weeks)
• Number of homework?
• Avg grades
• Avg goals
• Time taken to code the....
  • frontend
  • backend
  • presentation website
• Contributors
  • links to GH accounts
  • names

This could be used by both schoolsyst/presentation and schoolsyst/frontend (in the footer)