[config/irc] Add proper NickServ identification status checking for admins,
add delete functionality to config.

On use of an admin command, Michiru will now check the identification cache
first. If the nickname is not present in there, Michiru will run a WHOIS on
the nickname and check for any lines indicating NickServ identification
status. The cache is invalidated on nick change, part, kick or quit.

On the configuration end, `config.getlist` is renamed to `config.list` and
`config.delete(item, key, server=None, channel=None)` is added to support
flexibly removing items from dicts or lists/sets.

This commit also introduces a more flexible syntax in core.py for setting
configuration options, allowing you to prefix the configuration item name with
<channel>: or even <server>:<channel>: to set the option for that specific
channel or server, channel combination.

`bot.admin` has also been renamed to `bot.is_admin`.
[modules/uribot] Update uribot for config.getlist -> config.list API change.
[modules/waitopiggu] Add waitopiggu module.

This module allows you to configure Michiru to automatically ban a joining user
that is present on (one or more) configurable channels. This allows you to
efficiently deal with 'raids' or generally unpleasant source atmospheres.
This module needs to be explicitly enabled, as it is not by default.

Configuration values introduced:
- waitopiggu_whitelist: A nickname whitelist of people who will not be affected
   by this module.
- waitopiggu_channels: A list of 'bad' source channels, upon which a joining
   user will be banned if one or more occurs in their WHOIS list.
- waitopiggu_ban_method: Michiru can ban users using two methods: a direct
   host (`direct`) mask ban (which will use `*!*@host`), or a 'ban proxy'
   (`proxy`), causing Michiru to send a certain formatted private message to
   another user who will supposedly ban the offending user, or just log their
   existence, or do whatever they feel is appropriate.
- waitopiggu_ban_proxy: The nickname of the user that will be private messaged
   when using the `proxy` ban method.
- waitopiggu_ban_proxy_format: The message format that shall be used when
   private messaging the ban proxy when using the `proxy` ban method. This
   string shall be formatted according to Python's advanced string formatting
   (the `.format` method), and be filled in with the `{nick}`, `{server}`,
   `{channel}` and `{message}` variables. See below for what the `message`
   variable means.
- waitopiggu_ban_message: The ban message. When using the `direct` ban method
   this will be the kick message, or if using the `proxy` method it will be
   available in the formatted message string as `{message}`.