Migrate ban handling to server extensions/scripts

[wipe2238]

• [ ] bool player_connect( uint ip, string& message ) handle IP bans, called just before hardcoded checks (which will be removed after migration); called much earlier than player_registration and little earlier than player_login if function returns false, client receives FOGAME.MSG/1043 first, then message content (if not empty)
• [ ] provide extension/script for handling ban entries depends on #20 progress