Add a 'ParseTemplate' method on view engines to manually parse and add a template from a text

examples at: https://github.com/kataras/iris/tree/master/_examples/view/parse-template

relative to: https://github.com/kataras/iris/issues/1617

_examples/view/parse-template/amber/main.go

@@ -0,0 +1,28 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	e := iris.Amber(nil, ".amber") // You can still use a file system though.
+	e.AddFunc("greet", func(name string) string {
+		return "Hello, " + name + "!"
+	})
+	err := e.ParseTemplate("program.amber", []byte(`h1 #{ greet(Name) }`))
+	if err != nil {
+		panic(err)
+	}
+
+	app := iris.New()
+	app.RegisterView(e)
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.amber", iris.Map{
+		"Name": "Gerasimos",
+		// Or per template:
+		// "greet": func(....)
+	})
+}

_examples/view/parse-template/django/main.go

@@ -0,0 +1,26 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	e := iris.Django(nil, ".html") // You can still use a file system though.
+	e.AddFunc("greet", func(name string) string {
+		return "Hello, " + name + "!"
+	})
+	err := e.ParseTemplate("program.html", []byte(`<h1>{{greet(Name)}}</h1>`))
+	if err != nil {
+		panic(err)
+	}
+
+	app := iris.New()
+	app.RegisterView(e)
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.html", iris.Map{
+		"Name": "Gerasimos",
+	})
+}

_examples/view/parse-template/handlebars/main.go

@@ -0,0 +1,24 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	e := iris.Handlebars(nil, ".html") // You can still use a file system though.
+	e.ParseTemplate("program.html", `<h1>{{greet Name}}</h1>`, iris.Map{
+		"greet": func(name string) string {
+			return "Hello, " + name + "!"
+		},
+	})
+
+	app := iris.New()
+	app.RegisterView(e)
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.html", iris.Map{
+		"Name": "Gerasimos",
+	})
+}

_examples/view/parse-template/jet/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"reflect"
+
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/view"
+)
+
+func main() {
+	e := iris.Jet(nil, ".jet") // You can still use a file system though.
+	e.AddFunc("greet", func(args view.JetArguments) reflect.Value {
+		msg := "Hello, " + args.Get(0).String() + "!"
+		return reflect.ValueOf(msg)
+	})
+	err := e.ParseTemplate("program.jet", `<h1>{{greet(.Name)}}</h1>`)
+	if err != nil {
+		panic(err)
+	}
+
+	app := iris.New()
+	app.RegisterView(e)
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.View("program.jet", iris.Map{
+		"Name": "Gerasimos",
+	})
+}

_examples/view/parse-template/main.go

@@ -1,22 +1,28 @@
 // Package main shows how to parse a template through custom byte slice content.
+// The following works with HTML, Pug and Ace template parsers.
+// To learn how you can manually parse a template from a text for the rest
+// template parsers navigate through the example's subdirectories.
 package main
 
 import "github.com/kataras/iris/v12"
 
 func main() {
-	app := iris.New()
 	// To not load any templates from files or embedded data,
 	// pass nil or empty string on the first argument:
-	// view := iris.HTML(nil, ".html")
+	// e := iris.HTML(nil, ".html")
 
-	view := iris.HTML("./views", ".html")
-	view.ParseTemplate("program.html", []byte(`<h1>{{greet .Name}}</h1>`), iris.Map{
+	e := iris.HTML("./views", ".html")
+	// e := iris.Pug("./views",".pug")
+	// e := iris.Ace("./views",".ace")
+	e.ParseTemplate("program.html", []byte(`<h1>{{greet .Name}}</h1>`), iris.Map{
 		"greet": func(name string) string {
 			return "Hello, " + name + "!"
 		},
 	})
 
-	app.RegisterView(view)
+	app := iris.New()
+	app.RegisterView(e)
+
 	app.Get("/", index)
 	app.Get("/layout", layout)
 

_examples/view/template_handlebars_0/main.go

@@ -10,13 +10,13 @@ func main() {
 	app.Logger().SetLevel("debug")
 
 	// Init the handlebars engine
-	engine := iris.Handlebars("./templates", ".html").Reload(true)
+	e := iris.Handlebars("./templates", ".html").Reload(true)
 	// Register a helper.
-	engine.AddFunc("fullName", func(person map[string]string) string {
+	e.AddFunc("fullName", func(person map[string]string) string {
 		return person["firstName"] + " " + person["lastName"]
 	})
 
-	app.RegisterView(engine)
+	app.RegisterView(e)
 
 	app.Get("/", func(ctx iris.Context) {
 		viewData := iris.Map{