Implement IRC portion of Bancho

[cg0]

Closes #25

This is a work in progress implementation:

• Can connect to IRC
• Can message between IRC and Bancho
• Support Bancho commands
• Can PM Bancho user from IRC
• Can PM IRC user from Bancho
• Can PM IRC user from IRC
• Make chat engine more generic for IRC and Bancho users
• Support password auth (user token like osu)
• Display IRC users in Bancho connected players - Optional for this ticket
• Support secure IRC - Optional for this ticket
• Manually test common IRC clients (Only testing versions with Linux client):
  • HexChat
  • ircII
  • KVIrc
• Wire up event system for IRC
• Properly unit test
• Match osu! IRC implementation as best we can

[cg0]

Unit testing should require a basic IRC library for testing connections

[cg0]

For this implementation since the web frontend doesn't even support logging in yet we will have the IRC token be a Bancho command

[cg0]

For the event system since we already support chat events that come from Bancho it might be good to support a specific IRC chat event and move to also having a generic chat event to cover both grounds.

Edit: Too much work, just made generic

[cg0]

Seems the correct response to an incorrect password or no password given when required is to respond with ERR_PASSWDMISMATCH however that doesn't prompt the user to re-enter a password on HexChat which seems like it would be expected behaviour.

Message will need to be ammended to say what to do to get your password and let the user know to set it but it needs to be looked into if that's the only solution.

Edit: Some clients prompt afterwards

[cg0]

This will still require some additional work to move away from IRC and Bancho holding their own state of users to a centralised users map under the chat engine. However I feel this ticket has gone on for long enough.

See #215 and #216