Clearing up some dead code and adding docs to what-changed

Signed-off-by: Dave Shanley <dave@quobix.com>

what-changed/model/extensions.go

@@ -13,6 +13,7 @@ type ExtensionChanges struct {
 	PropertyChanges
 }
 
+// TotalChanges returns the total number of object extensions that were made.
 func (e *ExtensionChanges) TotalChanges() int {
 	return e.PropertyChanges.TotalChanges()
 }