Dir based plugins

[lucyllewy]

I've used typescript for this PR so running the bot will require compiling the .ts files into .js first.

Plugins are all stored in ./plugins/<messageType>/<arbitraryName>.

The messageType is any IRC message type as sent from irc.Client (the bot object) in it's events. i.e. if you would normally handle with code like:

bot.addEventListener('registered', function(message: string) {
    // handle the registered event
});

Then you can instead add a file into ./plugins/registered with content similar to:

export default (bot: irc.Client) => {
    return ([message]: [string]) => {
        // Handle the event here
    }
}

You need to have an export called default which is a function accepting a single argument to store the bot object. This function should then return a closure which accepts the arguments appropriate for the specific event the plugin is handling as raised by the irc module.