resources: Officially add Validate method

This officially adds the Validate method to the resource API, and also
cleans up the ordering in existing resources.

resources/pkg.go

@@ -67,6 +67,15 @@ func (obj *PkgRes) Default() Res {
 	}
 }
 
+// Validate checks if the resource data structure was populated correctly.
+func (obj *PkgRes) Validate() error {
+	if obj.State == "" {
+		return fmt.Errorf("State cannot be empty!")
+	}
+
+	return nil
+}
+
 // Init runs some startup code for this resource.
 func (obj *PkgRes) Init() error {
 	obj.BaseRes.kind = "Pkg"
@@ -102,15 +111,6 @@ func (obj *PkgRes) Init() error {
 	return nil
 }
 
-// Validate checks if the resource data structure was populated correctly.
-func (obj *PkgRes) Validate() error {
-	if obj.State == "" {
-		return fmt.Errorf("State cannot be empty!")
-	}
-
-	return nil
-}
-
 // Watch is the primary listener for this resource and it outputs events.
 // It uses the PackageKit UpdatesChanged signal to watch for changes.
 // TODO: https://github.com/hughsie/PackageKit/issues/109