Added more ICCC commands

+ Added ICCC command for register a host
+ Added ICCC command for register a command i.e. listener
+ Added ICCC command for getting a number from NumGen

ICCC/SystemMessages/ICCCRegisterHost.go

@@ -0,0 +1,7 @@
+package SystemMessages
+
+// The message to register a host to ICCC.
+type ICCCRegisterHost struct {
+	Hostname      string // The hostname for the end-point
+	IPAddressPort string // The IP address and port for the end-point
+}