Add: LAN mode with fixed hour (option), user defined nicknames

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Just to make multiuser easier to use in my house, I've added a simple "LAN mode".

Also:

• command line arguments, parsing and help messages.
• set the hour and make time move very, very slowly (basically fixed hour).
• set the seed (not sure that works or is useful).
• /nick command to pick arbitrary nicknames (LAN mode only).

Important: Do not use LAN mode on the public internet! You will get nothing but grief.