chore: Make field declarations explicit

This used to be valid code:

```
class Foo {
  constructor() {
    this.bar = ‘string’;
  }
}
```

This will now fail since ‘bar’ is not explicitly
defined as a field. We now have to write:

```
class Foo {
  bar:string; // << REQUIRED
  constructor() {
    this.bar = ‘string’;
  }
}
```

modules/facade/src/lang.dart

@@ -159,3 +159,6 @@ dynamic getMapKey(value) {
   return value.isNaN ? _NAN_KEY : value;
 }
 
+normalizeBlank(obj) {
+  return isBlank(obj) ? null : obj;
+}

modules/facade/src/lang.es6

@@ -194,3 +194,7 @@ export function looseIdentical(a, b):boolean {
 export function getMapKey(value) {
   return value;
 }
+
+export function normalizeBlank(obj) {
+  return isBlank(obj) ? null : obj;
+}