New player welcome message for lobby

[Crystalwarrior]

I think it would be nice to have a welcome message for ao lobby to greet new players and serve as a guide. Bonus points if it's capable of playing back a demo format (timed messages, etc. so you can have an intro cutscene or something)

This flag will be set per ipid, can be interrupted with an ooc command, or played again by a different command.

This feature would allow servers to create their own customized "teasers" to explain how the server works in a fun and hopefully minimally obtrusive way while not spamming info. Additionally this cinematic should play only for the joining client, and should only start when the client picks a character!