VOL-2452: Add new omci get functions

- Provide functions that encode omci get responses needed
  to lookup a MIB template.  Other fields added for completeness

Change-Id: I906cb0559afe40f0c4ab31bb44ff09135738823f
diff --git a/omci_defs.go b/omci_defs.go
index d84e878..90ea0af 100644
--- a/omci_defs.go
+++ b/omci_defs.go
@@ -159,10 +159,14 @@
 
 func (c OmciClass) PrettyPrint() string {
 	switch c {
+	case SoftwareImage:
+		return "SoftwareImage"
 	case EthernetPMHistoryData:
 		return "EthernetPMHistoryData"
 	case ONUG:
 		return "ONUG"
+	case ONU2G:
+		return "ONU2G"
 	case ANIG:
 		return "ANIG"
 	case GEMPortNetworkCTP:
@@ -175,8 +179,10 @@
 
 const (
 	// Managed Entity Class values
+	SoftwareImage         OmciClass = 7
 	EthernetPMHistoryData OmciClass = 24
 	ONUG                  OmciClass = 256
+	ONU2G                 OmciClass = 257
 	ANIG                  OmciClass = 263
 	GEMPortNetworkCTP     OmciClass = 268
 )