Quiz for Diamond DA50 added.

Added quiz for DA40NG

Added quiz for 8KCAB (Decathlon used for FI and UPRT training).
Introduced dark mode (based on system settings).

Reintroduced PA31 quiz and some other minor improvements.

Reintroduced the PA31 quiz

Online storage of certificates

Very minor changes this time:
- Fix to Norwegian aptitude quiz (correct answer not available).
- Added URL to osloflightacademy.no on first page.

Added quiz and simplified login process.

Updated quizes.

Added two new quizes in Norwegian (DA40D and Pilot Aptitude Fun Quiz)