Implements support for receiving chat messages from the server, the
first step towards #63 chat support. Long way to go, but is a start.
* server: handle ServerMessage_* packets, on_servermessage
* format: get the with arguments of translations
* format: hardcode chat types
* format: support bare strings, used in chat.type.text
* format: use extra text if present, fixes missing username on 1.16.5
* console/main/server: activate on receiving chat messages