SEBA-699 validate core version

Change-Id: I2ee14504c71e9fb4ecb262c9247108261c76fad3
diff --git a/commands/command.go b/commands/command.go
index bdd7dfb..91d44a9 100644
--- a/commands/command.go
+++ b/commands/command.go
@@ -37,6 +37,8 @@
 	OUTPUT_TABLE OutputType = iota
 	OUTPUT_JSON
 	OUTPUT_YAML
+
+	CORE_VERSION_CONSTRAINT = ">= 3, < 4" // Support XOS major version 3
 )
 
 // Make it easy to override output stream for testing