Implemented the ability to set the server to only allow registered
users.  Also updated client to reflect the log-in rejection as well as
put a check in place for the server to not start if db connection is not
available yet registration is required.

Specifically this should cover people connecting with a username of
"\u200C"

improved code for automatic joining of persistent games; disconnecting + reconnecting works as it should with ISL

added mutex for RNG, moved game command implementation from S_PH to S_Player in preparation for forwarding of game commands via tunneling interface