Track channel join times, use them to optionally enforce history access
restrictions

enable the use of grouped nicks as account names for SASL,
if force-nick-equals-account is disabled

Store the channel-user modes of always-on clients along with their
channel memberships, restore them on server startup. This will coexist
alongside /CS AMODE, which autoapplies modes to clients on join regardless
of their always-on status.

NS SUSPEND DEL incorrectly required the use of the casefolded account name.

Fixes #1380

Enhancements to NS SUSPEND, including stored metadata and the ability
to list suspensions

0. Enable email verification
1. Register `dog`
2. Register `d0g`
3. Verify `dog`
4. Verify `d0g`: verification succeeds but the nick cannot be used

See discussion on #68.

don't need to send account-notify * (logout notification)
because either we never sent the initial account-notify
(if we are being logged out as part of fixupNickEqualsAccount)
or else we are immediately going to kill the client
(if we are being logged out as part of unregister/erase)

This avoids conditions where two sessions can be attached to the same client
while not logged into an account.

These commands search the registered nicknames/channels for ones
matching the provided regex, or return the entire list.

Only operators with chanreg (for ChanServ) or accreg (for NickServ)
capabilities can use LIST.