extract the Delim for redis sessiondb as requested at https://github.com/kataras/iris/issues/1256 and add a mvc/regexp example and some other trivial changes

Former-commit-id: f9e09320bfe07ae10ac74f54a78272cf21d21cc7

_examples/mvc/regexp/main.go

@@ -0,0 +1,49 @@
+// Package main shows how to match "/xxx.json" in MVC handler.
+package main
+
+/*
+There is no MVC naming pattern for such these things,you can imagine the limitations of that.
+Instead you can use the `BeforeActivation` on your controller to add more advanced routing features
+(https://github.com/kataras/iris/tree/master/_examples/routing).
+
+You can also create your own macro,
+i.e: /{file:json} or macro function of a specific parameter type i.e: (/{file:string json()}).
+Read the routing examples and you will gain a deeper view, there are all covered.
+*/
+
+import (
+	"github.com/kataras/iris"
+	"github.com/kataras/iris/mvc"
+)
+
+func main() {
+	app := iris.New()
+
+	mvcApp := mvc.New(app.Party("/module"))
+	mvcApp.Handle(new(myController))
+
+	// http://localhost:8080/module/xxx.json (OK)
+	// http://localhost:8080/module/xxx.xml  (Not Found)
+	app.Run(iris.Addr(":8080"))
+}
+
+type myController struct{}
+
+func (m *myController) BeforeActivation(b mvc.BeforeActivation) {
+	// b.Dependencies().Add/Remove
+	// b.Router().Use/UseGlobal/Done // and any standard API call you already know
+
+	// 1-> Method
+	// 2-> Path
+	// 3-> The controller's function name to be parsed as handler
+	// 4-> Any handlers that should run before the HandleJSON
+
+	// "^[a-zA-Z0-9_.-]+.json$)" to validate file-name pattern and json
+	// or just:  ".json$" to validate suffix.
+
+	b.Handle("GET", "/{file:string regexp(^[a-zA-Z0-9_.-]+.json$))}", "HandleJSON" /*optionalMiddleware*/)
+}
+
+func (m *myController) HandleJSON(file string) string {
+	return "custom serving of json: " + file
+}