Add a third, simple, example for folder structuring as requested at https://github.com/kataras/iris/issues/748

One change to code base but it will be described at the next version:

Error Handlers (`app.OnErrorCode/OnAnyErrorCode`)  respect the `app.UseGlobal`'s middlewares now (not the `app.Use` for reasons we can all understand, hopefully).


Former-commit-id: ec97bbb04548f9932cf4d7b950be513b70747bcb

_examples/structuring/handler-based/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"github.com/kataras/iris/_examples/structuring/handler-based/bootstrap"
+	"github.com/kataras/iris/_examples/structuring/handler-based/middleware/identity"
+	"github.com/kataras/iris/_examples/structuring/handler-based/routes"
+)
+
+var app = bootstrap.New("Awesome App", "kataras2006@hotmail.com",
+	identity.Configure,
+	routes.Configure,
+)
+
+func init() {
+	app.Bootstrap()
+}
+
+func main() {
+	app.Listen(":8080")
+}