[ADD] component: implement t-model directive

closes #170

tools/playground/samples.js

@@ -1292,6 +1292,60 @@ const app = new App({qweb});
 app.mount(document.body);
 `;
 
+const FORM = `class Form extends owl.Component {
+    state = {
+        text: "",
+        othertext: "",
+        number: 11,
+        color: "",
+        bool: false
+    };
+}
+
+const qweb = new owl.QWeb(TEMPLATES);
+const form = new Form({ qweb });
+form.mount(document.body);
+`;
+
+const FORM_XML = `<templates>
+   <div t-name="Form">
+        <h1>Form</h1>
+        <div>
+          Text (immediate): <input t-model="text"/>
+        </div>
+        <div>
+          Other text (lazy): <input t-model.lazy="othertext"/>
+        </div>
+        <div>
+          Number: <input  t-model.number="number"/>
+        </div>
+        <div>
+          Boolean: <input  type="checkbox" t-model="bool"/>
+        </div>
+        <div>
+          Color, with a select: <select  t-model="color">
+            <option value="">Select a color</option>
+            <option value="red">Red</option>
+            <option value="blue">Blue</option>
+          </select>
+        </div>
+        <div>
+          Color, with radio buttons:
+            <span><input type="radio" name="color" id="red" value="red" t-model="color"/><label for="red">Red</label></span>
+            <span><input type="radio" name="color" id="blue" value="blue" t-model="color"/><label for="blue">Blue</label></span>
+        </div>
+
+        <hr/>
+        <h1>State</h1>
+        <div>Text: <t t-esc="state.text"/></div>
+        <div>Other Text: <t t-esc="state.othertext"/></div>
+        <div>Number: <t t-esc="state.number"/></div>
+        <div>Boolean: <t t-if="state.bool">True</t><t t-else="1">False</t></div>
+        <div>Color: <t t-esc="state.color"/></div>
+    </div>
+</templates>
+`;
+
 export const SAMPLES = [
   {
     description: "Click Counter",
@@ -1305,6 +1359,11 @@ export const SAMPLES = [
     xml: CLICK_COUNTER_XML,
     css: CLICK_COUNTER_CSS
   },
+  {
+    description: "Form input bindings",
+    code: FORM,
+    xml: FORM_XML,
+  },
   {
     description: "Widget Composition",
     code: WIDGET_COMPOSITION,