Server/PacketIO: Updated CMSG/SMSG_GROUP_INVITE structures and opcodes.
Server/PacketIO: Updated SMSG_PARTY_COMMAND_RESULT opcode.
Server/PacketIO: Updated CMSG_GROUP_INVITE_RESPONSE structure and opcode.
Server/PacketIO: Updated SMSG_GROUP_DECLINE opcode.
Server/PacketIO: Updated SMSG_GROUP_LIST structure and opcode.
Server/PacketIO: Updated SMSG_GROUP_DESTROYED opcode.