installer: refactor App interface
diff --git a/core/installer/app_manager.go b/core/installer/app_manager.go
index bf9dbe2..05cb496 100644
--- a/core/installer/app_manager.go
+++ b/core/installer/app_manager.go
@@ -59,8 +59,8 @@
 	if err != nil {
 		return err
 	}
-	namespaces := make([]string, len(app.Namespaces))
-	for i, n := range app.Namespaces {
+	namespaces := make([]string, len(app.Namespaces()))
+	for i, n := range app.Namespaces() {
 		ns, err := ns.Generate(n)
 		if err != nil {
 			return err
@@ -91,7 +91,7 @@
 	fmt.Printf("%+v\n", derived)
 	err = m.repoIO.InstallApp(
 		app,
-		filepath.Join(appDir, app.Name+suffix),
+		filepath.Join(appDir, app.Name()+suffix),
 		config,
 		derived,
 	)