Removed m_save_session, some code cleanup.
Added online name of the player to be logged in/out to the sign in/out
message.
Added support to change the online account for the same player.
When a player logs in with an online account, reset any other saved
session for this online account (since these token are now invalid).
Added support for player icons.
Support old configs (i.e. if icons don't exist, they will be
created at startup).