[REQ] Some admin commands missing

[crashzk]

• !say <message> - Say message as admin in chat // (ADMFLAG_CHAT)
  • It would be interesting to have the option to add @ before messages, both in say and say_team (say_team sends the message only to admins)
• !psay <#userid or name> <message> - Sends private message to player // (ADMFLAG_CHAT)
• !banip <ip> [time in minutes/0 perm] [reason] - Ban player via IP address // (ADMFLAG_BAN)
• !cvar <cvar> <value> - Change cvar value // (ADMFLAG_CONVARS)