[IMP] component: various prop validation improvements

- add optional form for list props: ['optionalField?']
- accept undefined values for optional props
- allow declaring props with only boolean true
- throw error if extra prop is given to component

closes #223

tests/__snapshots__/component.test.ts.snap

@@ -353,7 +353,7 @@ exports[`class and style attributes with t-component t-att-class is properly add
     let def3;
     const ref5 = \`child\`;
     let _6 = {'a':true};
-    Object.assign(_6, this.utils.toObj(context['state'].b?'b':''))
+    Object.assign(_6, utils.toObj(context['state'].b?'b':''))
     let w4 = 4 in context.__owl__.cmap ? context.__owl__.children[context.__owl__.cmap[4]] : false;
     let _2_index = c1.length;
     c1.push(null);

tests/__snapshots__/props_validation.test.ts.snap

@@ -0,0 +1,43 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`props validation props are validated in dev mode (code snapshot) 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.utils;
+    let QWeb = this.constructor;
+    let owner = context;
+    var h = this.utils.h;
+    let c1 = [], p1 = {key:1};
+    var vn1 = h('div', p1, c1);
+    //COMPONENT
+    let def3;
+    let w4 = 4 in context.__owl__.cmap ? context.__owl__.children[context.__owl__.cmap[4]] : false;
+    let _2_index = c1.length;
+    c1.push(null);
+    let props4 = {message:1};
+    if (w4 && w4.__owl__.renderPromise && !w4.__owl__.vnode) {
+        if (utils.shallowEqual(props4, w4.__owl__.renderProps)) {
+            def3 = w4.__owl__.renderPromise;
+        } else {
+            w4.destroy();
+            w4 = false;
+        }
+    }
+    if (!w4) {
+        let componentKey4 = \`Child\`;
+        let W4 = context.components && context.components[componentKey4] || QWeb.components[componentKey4];
+        if (!W4) {throw new Error('Cannot find the definition of component \\"' + componentKey4 + '\\"')}
+        utils.validateProps(W4, props4)
+        w4 = new W4(owner, props4);
+        context.__owl__.cmap[4] = w4.__owl__.id;
+        def3 = w4.__prepare();
+        def3 = def3.then(vnode=>{let pvnode=h(vnode.sel, {key: 4, hook: {insert(vn) {let nvn=w4.__mount(vnode, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w4.destroy();}}});c1[_2_index]=pvnode;w4.__owl__.pvnode = pvnode;});
+    } else {
+        utils.validateProps(w4.constructor, props4)
+        def3 = def3 || w4.__updateProps(props4, extra.forceUpdate, extra.patchQueue);
+        def3 = def3.then(()=>{if (w4.__owl__.isDestroyed) {return};let pvnode=w4.__owl__.pvnode;c1[_2_index]=pvnode;});
+    }
+    extra.promises.push(def3);
+    return vn1;
+}"
+`;