create the new FileServer and HandleDir, deprecate the rest APIBuilder/Party static methods and more

relative: https://github.com/kataras/iris/issues/1283 and removing pongo2 from vendor: https://github.com/kataras/iris/issues/1284

Former-commit-id: 3ec57b349f99faca2b8e36d9f7252db0b6ea080d

_examples/file-server/embedding-files-into-app/main.go

@@ -14,8 +14,14 @@ import (
 // See `file-server/embedding-gziped-files-into-app` example as well.
 func newApp() *iris.Application {
 	app := iris.New()
+	app.Logger().SetLevel("debug")
 
-	app.StaticEmbedded("/static", "./assets", Asset, AssetNames)
+	app.HandleDir("/static", "./assets", iris.DirOptions{
+		Asset:      Asset,
+		AssetInfo:  AssetInfo,
+		AssetNames: AssetNames,
+		ShowList:   true,
+	})
 
 	return app
 }