Refactor/credentials: work with a single credential

[MrAnderson]

I still really like RFC Possibility SQRL

and

SQRL - Secure Quick Reliable Login

SQRL is almost finished [Security Now 562: IoT Infancy] But there is something, whenever you type a correct character it’s indicated with green, I’ve learned from the SAFE Network approach, that you never reveal if something is correct or not. So that might be a issue… It will also have Yubico support