[IMP] component: simplify constructor API

It now takes two arguments: parent (optional, only for non-root
components) and props (optional). In the case of the root component,
the env is taken from the config (config.defaultEnv). If it doesn't
exists, the default env is created on the fly.

Closes #306

tools/playground/samples.js

@@ -16,9 +16,7 @@ class App extends Component {
 App.components = { Greeter };
 
 // Application setup
-// Note that the xml templates are injected into the global TEMPLATES variable.
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({ qweb });
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -70,8 +68,7 @@ class App extends Component {
 }
 App.components = { Counter };
 
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({qweb});
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -228,8 +225,7 @@ class App extends Component {
 }
 App.components = { DemoComponent };
 
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({ qweb });
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -298,8 +294,7 @@ class App extends owl.Component {
 }
 
 // Application setup
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({ qweb });
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -349,11 +344,9 @@ const themeContext = new Context({
    background: '#000',
    foreground: '#fff',
 });
-const env = {
-    qweb: new owl.QWeb({ templates: TEMPLATES}),
-    themeContext: themeContext,
-};
-const app = new App(env);
+// Add the themeContext the environment to make it available to all components
+owl.config.env.themeContext = themeContext;
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -534,26 +527,25 @@ TodoApp.components = { TodoItem };
 //------------------------------------------------------------------------------
 // App Initialization
 //------------------------------------------------------------------------------
-function saveState(state) {
-    const str = JSON.stringify(state);
-    window.localStorage.setItem(LOCALSTORAGE_KEY, str);
-}
 
-function loadState() {
-    const localState = window.localStorage.getItem(LOCALSTORAGE_KEY);
-    return localState ? JSON.parse(localState) : initialState;
-}
+function makeStore() {
+    function saveState(state) {
+        const str = JSON.stringify(state);
+        window.localStorage.setItem(LOCALSTORAGE_KEY, str);
+    }
+    function loadState() {
+        const localState = window.localStorage.getItem(LOCALSTORAGE_KEY);
+        return localState ? JSON.parse(localState) : initialState;
+    }
 
-function makeEnv() {
     const state = loadState();
     const store = new owl.Store({ state, actions });
     store.on("update", null, () => saveState(store.state));
-    const qweb = new owl.QWeb({ templates: TEMPLATES});
-    return { qweb, store };
+    return store;
 }
 
-const env = makeEnv();
-const app = new TodoApp(env);
+owl.config.env.store = makeStore();
+const app = new TodoApp();
 app.mount(document.body);
 `;
 
@@ -1040,12 +1032,9 @@ function setupResponsivePlugin(env) {
 //------------------------------------------------------------------------------
 // Application Startup
 //------------------------------------------------------------------------------
-const env = {
-    qweb: new owl.QWeb({ templates: TEMPLATES}),
-};
-setupResponsivePlugin(env);
+setupResponsivePlugin(owl.config.env);
 
-const app = new App(env);
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -1187,8 +1176,7 @@ class App extends Component {
 App.components = {Card, Counter};
 
 // Application setup
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({ qweb });
+const app = new App();
 app.mount(document.body);`;
 
 const SLOTS_XML = `<templates>
@@ -1301,10 +1289,9 @@ class App extends Component {
         }, 3000);
     }
 }
-App.components = {SlowComponent, NotificationList};
+App.components = {SlowComponent, NotificationList, AsyncRoot};
 
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const app = new App({ qweb });
+const app = new App();
 app.mount(document.body);
 `;
 
@@ -1373,8 +1360,7 @@ class Form extends Component {
 }
 
 // Application setup
-const qweb = new owl.QWeb({ templates: TEMPLATES});
-const form = new Form({ qweb });
+const form = new Form();
 form.mount(document.body);
 `;
 
@@ -1540,7 +1526,6 @@ class App extends Component {
 }
 App.components = { WindowManager };
 
-const qweb = new owl.QWeb({ templates: TEMPLATES});
 const windows = [
   {
     name: "Hello",
@@ -1558,8 +1543,8 @@ const windows = [
   }
 ];
 
-const env = { qweb, windows };
-const app = new App(env);
+owl.config.env.windows = windows;
+const app = new App();
 app.mount(document.body);
 `;