Support ScuttleButt keypair as credentials (duplicate #796)
ScuttleButt is a p2p social network of a new kind.
The ScuttleButt keypair created in $HOME/.ssb folder use the same elliptic algorithm than Duniter Ğ1.
So it is easy to handle an account using the ssb keypair as credentials.
For a start, just add a "Add account from scuttlebut account" button.