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

cache/browser.go

@@ -92,7 +92,7 @@ const ifNoneMatchHeaderKey = "If-None-Match"
 //
 // Usage with combination of `StaticCache`:
 // assets := app.Party("/assets", cache.StaticCache(24 * time.Hour), ETag)
-// assets.StaticWeb("/", "./assets") or StaticEmbedded("/", "./assets") or StaticEmbeddedGzip("/", "./assets").
+// assets.HandleDir("/", "./assets")
 //
 // Similar to `Cache304` but it doesn't depends on any "modified date", it uses just the ETag and If-None-Match headers.
 //
@@ -124,7 +124,7 @@ var ETag = func(ctx context.Context) {
 // by watching system directories changes manually and use of the `ctx.WriteWithExpiration`
 // with a "modtime" based on the file modified date,
 // can be used on Party's that contains a static handler,
-// i.e `StaticWeb`, `StaticEmbedded` or even `StaticEmbeddedGzip`.
+// i.e `HandleDir`.
 var Cache304 = func(expiresEvery time.Duration) context.Handler {
 	return func(ctx context.Context) {
 		now := time.Now()