Allow the user to pick a player name for offline mode.
Big auth refactor. Now using session objects instead of the accounts themselves.
Sessions only last for one instance start and hold all the auth and player data.
Refactor MojangAccount so it exposes a less generic interface and supports login. Hide the ugly details.
Yggdrasil tasks are now only used from MojangAccount.
Auth uses the refresh endpoint instead of validate. This means less password entering.
Console will now only autoscroll when already scrolled all the way down.
Better conformance with the Yggdrasil auth protocol (not complete yet, but Mojang launcher isn't complete either).
Fix bug that prevented saving the account data (uninitialized variable).
Accounts can now trigger account list saving, this is used for the refresh endpoint.
