PSA: Change in registration (new captcha/questions) + possible migration

[Peter]

- I have removed ReCAPTCHA as a few users have expressed their distaste in it. And I totally understand why. Sadly it didn't really defeat spammers either.
- We'll possibly migrate to phpBB as SMF has not received any updates for several .... years now? Besides minor fixes, that is. It's still in the work, if the migration actually happens, I'll put the forum in maintenance mode to avoid any lost posts.