Fixed template guid not being serialized

com.unity.perception/Runtime/GroundTruth/Labelers/KeyPointTemplate.cs

         /// <summary>
         /// The <see cref="Guid"/> of the template
         /// </summary>
-        public Guid templateID;
+        public string templateID = Guid.NewGuid().ToString();
         /// <summary>
         /// The name of the template
         /// </summary>

com.unity.perception/Tests/Runtime/GroundTruthTests/KeyPointGroundTruthTests.cs

             };
 
             var template = ScriptableObject.CreateInstance<KeyPointTemplate>();
-            template.templateID = guid;
+            template.templateID = guid.ToString();
             template.templateName = label;
             template.jointTexture = null;
             template.skeletonTexture = null;