Create gateway RpcSocket service

[NatalieWolfe]

Gateway requirements:

• Listen for socket.io connections on /gateway.
• Wait for client to emit registration event.
• Limit registration wait to n seconds.
• Close connections for any clients which fail registration.
• On success, add client to registered pool.
• Forward all chat messages which match registered filter to the registered pool.
• Send chat messages whenever clients emit a message command.

Registration requirements:

• Client must provide all details as their first message after connecting.
• command: Must be register.
• service.name: Name of the service the client represents.
• filters: Array of filter definitions. May be empty to receive all messages.

Filter requirements:

• Filter properties are combined (&&).
• regex: Filter messages via regex.
• room_id: Filter messages by room.
• user_id: Filter messages by user.

Message command requirements:

• May be sent in either direction (client -> gateway -> tg or tg -> gateway -> client).
• Contains all information needed to process the message and reply to it.