Ability to register a view engine per group of routes or for the current a chain of handlers

Example at: https://github.com/kataras/iris/tree/master/_examples/view/context-view-engine

context/view.go

@@ -0,0 +1,22 @@
+package context
+
+import "io"
+
+// ViewEngine is the interface which all view engines should be implemented in order to be registered inside iris.
+type ViewEngine interface {
+	// Load should load the templates from a physical system directory or by an embedded one (assets/go-bindata).
+	Load() error
+	// ExecuteWriter should execute a template by its filename with an optional layout and bindingData.
+	ExecuteWriter(w io.Writer, filename string, layout string, bindingData interface{}) error
+	// Ext should return the final file extension which this view engine is responsible to render.
+	Ext() string
+}
+
+// ViewEngineFuncer is an addition of a view engine,
+// if a view engine implements that interface
+// then iris can add some closed-relative iris functions
+// like {{ url }}, {{ urlpath }} and {{ tr }}.
+type ViewEngineFuncer interface {
+	// AddFunc should adds a function to the template's function map.
+	AddFunc(funcName string, funcBody interface{})
+}