Implement basic commands on server and delete useless variables
Implement basic commands on server and delete useless variables

Useless variables deleted:
* *client-read-threads*
* *client-read-mutex*

Basic commands:
* /help => list the allowed commands
* /log => fetch the last 15 messages on server and return to client caller
* /quit => just exit the client
* /users => fetch user lists online and return to client caller

ryukinix/lisp-chat,ryukinix/lisp-chat