Add support for account-notify, extended-join

Add support for account-notify, extended-join

Add support for account-notify to track account changes and
extended-join to get account information on join.  For now, this only
updates user/hostname information.  In the future it will track
logged in accounts in ircuser, pending a new feature flag and
inclusion of WHOX support.

See http://ircv3.net/specs/extensions/account-notify-3.1.html
And http://ircv3.net/specs/extensions/extended-join-3.1.html