Adding login forwarding via config

This is a second attempt at https://github.com/RJ/irccat/pull/11

Added code to send "login" (the users ident) to the command handler. We needed this to be able to compare the user's ident on a private IRC server.

This can be enabled by including this in the config xml:
````
<fields>
    <includelogin>true</includelogin>
</fields>
````

Without this setting in the config, it should be backwards compatible.