Add multi account support

[cm-t 🦄🏂🌈🎵]

The client should allow user to setup and use maby account.

(example user case: One personnal account, an other for my LoCo, etc...)

Note: Since user might have same account on different node, or different account of the same node, a custop label should be used to name each new account (like 'me@LoCo's node). This how it is handled in dekko.