Make gtfo command drop connection immediately

Always send QUIT command when dropping IRC connection.
Otherwise, it'll open a new connection to IRC while the
the IRC network still thinks the old connection is active
(even if the TCP connection is already closed). This
prevents the new one from acquiring the proper nick or
joining the channel.
Set Mumble user comment when IRC is disconnected

Instead of spamming Mumble chat with disconnect messages,
set a comment on the user to indicate the disconnection.
Once re-connected, remove the comment.
Can't IRC AWAY or Mumble comment before login

Don't allow the new mumble.setComment() and irc.setAway()
to send any packets until the connection is established
(i.e. logged in and channel joined). Doing it too early
could mess up the login sequence. The bot already has a
check like this in AbstractConnection.sendTextMessage().
Merge pull request #2 from thvortex/master

Lost IRC connection sets Mumble user comment