* Add METADATA command handler which currently only allows to modify a client's certificate fingerprint
* Minor reformatting and style inconsistency fixes

* Remove support for deprecated channel mode `u`
* Add support for channel mode `N`
* Fixed the `UID` message handler requiring the correct amount of arguments
* Fixed the `SID` message handler requiring the correct amount of arguments
* Fixed the `SJOIN` message handler requiring the correct amount of arguments
* Minor documentation updates and style corrections
* Remove pointless return statement in the `JOIN` message handler
* Add support for the owner and admin channel prefix modes
* Add support for `MLOCK`
* Fixed SendChannel() so modes are prefixed with a `+`
* Change SendJoin() to actually use the mode stacker
* Add support for channel mode `Q`
* Add support for channel mode `Z`
* Add support for user mode `B` and `Z`
* Actually user mode `g` is not oper only. For some reason this mode got set to oper only in anope/anope@1e625b6
* Work properly with extended bans, e.g. don't normalize masks starting with a `$`

This was made obsolete by the previous commit.

* Parse PROTOCTL PREFIX and PROTOCTL USERMODES
* Add several previously unhandled modes
* Fix incorrect SJOIN prefix handling
* Enable message tags sending from ircd
* Add timedban matcher
* Add operclass matcher
* Store all client and channel moddata.
* Call unreal's internal unban on /cs unban
* Check for ~a:0 ban
* Add country ban matcher
* Use +B umode for services bots

hybrid.cpp: adjust IsIdentValid test to comply with upcoming ircd-hybrid where
user names may only consist of [A-Za-z0-9._-] and may not begin with '.', '-',
or '_'.

As a side effect this fixes an issue where currently it is possible to introduce
bots whose user name starts with (non-alnum) characters considered invalid for
ircd-hybrid leading to a services shutdown due to a nick introduction/kill loop.