* fix #2002

`CS AMODE #channel +f nickname` is invalid, but was being accepted
incorrectly.

* simplify logic

CS AMODE changes should take immediate effect even if the nick
does not match the account.

CS PURGE should send a snomask

Reported by @mogad0n. If a user had both operator privileges and
channel owner privileges, the CS TRANSFER would proceed as though
unprivileged, requiring acceptance by the receiving user. Fix this
to not require acceptance.

Commit 7ce396931c introduced the ability
that every user with an account in the AMODE list of a channel can use
the OP command to restore their modes. Update the chanserv help message
accordingly.

Document permissions structure of CS AMODE

CS INFO with no arguments should list your registered channels

Implement the new bot mode spec:
https://github.com/ircv3/ircv3-specifications/pull/439

Improve error message for CS TRANSFER

Transition most "is an operator" checks to require a specific operator
capability

CS OP should regrant one's stored amode

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

Improve auditability of sensitive operator actions

1. Consolidate PURGE and UNPURGE into subcommands
2. Add PURGE LIST
3. PURGE ADD now requires a confirmation code

Fixes #1294

DEOP is now pure syntactic sugar for /mode #channel -o nick,
the change is attributed to the originating user and not to ChanServ.

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.

This propagates CS AMODE changes to the actual modes, but not the other
way around.

Also fixes #909.

* Fix #684
* Fix #683
* Add `CHANSERV CLEAR`
* Allow mode changes from channel founders even when they aren't joined
* Operators with the chanreg capability are exempt from max-channels-per-account
* Small fixes and cleanup

1. DRY "banner" descriptions of each services
2. `/HELP NICKSERV` now refers the user to `/NICKSERV HELP`, etc.
3. Fix double translation of `textGenerator` output

* limit the total number of registrations per account
* when an account is unregistered, unregister all its channels