Services: default NickServ and ChanServ to NickServ and ChanServ.

* Most of networks have services with this name.
    * I can only name QuakeNet from those that don't, but the default
    configuration exludes it.
* If this plugin is loaded in Supybot-wizard, it asks for nicknames of
NickServ and ChanServ.

[SKIP CI] because this is `git commit --amend` and the build already
passed.