[IMP] component: introduce OwlEvent

Closes #485

src/component/component.ts

@@ -1,4 +1,5 @@
 import { Observer } from "../core/observer";
+import { OwlEvent } from "../core/owl_event";
 import { CompiledTemplate, QWeb } from "../qweb/index";
 import { patch, VNode } from "../vdom/index";
 import "./directive";
@@ -388,7 +389,7 @@ export class Component<T extends Env, Props extends {}> {
    */
   trigger(eventType: string, payload?: any) {
     if (this.el) {
-      const ev = new CustomEvent(eventType, {
+      const ev = new OwlEvent(this, eventType, {
         bubbles: true,
         cancelable: true,
         detail: payload

src/core/owl_event.ts

@@ -0,0 +1,15 @@
+import { Component } from "../component/component";
+
+/**
+ * We define here OwlEvent, a subclass of CustomEvent, with an additional
+ * attribute:
+ *  - originalComponent: the component that triggered the event
+ */
+
+export class OwlEvent<T> extends CustomEvent<T> {
+  originalComponent: Component<any, any>;
+  constructor(component, eventType, options) {
+    super(eventType, options);
+    this.originalComponent = component;
+  }
+}