reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/pprof/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+
+	"github.com/kataras/iris/v12/middleware/pprof"
+)
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.HTML("<h1> Please click <a href='/debug/pprof'>here</a>")
+	})
+
+	p := pprof.New()
+	app.Any("/debug/pprof", p)
+	app.Any("/debug/pprof/{action:path}", p)
+	//                              ___________
+	app.Listen(":8080")
+}