Implement account-notify, extended-join and WHOX

Also integrate it with NickAuth.

Closes #778.
Fix tests
Fix typo
Fix previous commit
Add do352 back for IRCds which do not support WHOX
Fix code style
Re-add removed comment
NickAuth: Don't clear auth when joining unidentified
Merge pull request #804 from nyuszika7h/account-notify

Implement account-notify, extended-join and WHOX