feat(query): adds initial implementation of the query api.

Queries allow a directive to inject a live list of directives of a given
type from its LightDom. The injected list is Iterable (in JS and Dart).
It will be Observable when Observables are support in JS, for now it
maintains a simple list of onChange callbacks API.

To support queries, element injectors now maintain a list of
child injectors in the correct DOM order (dynamically updated by
viewports).

For performance reasons we allow only 3 active queries in an injector
subtree. The feature adds no overhead to the application when not
used. Queries walk the injector tree only during dynamic view
addition/removal as triggered by viewport directives.

Syncs changes between viewContainer on the render and logic sides.

Closes #792

modules/angular2/src/core/annotations/di.js

@@ -54,3 +54,15 @@ export class Attribute extends DependencyAnnotation {
     return this;
   }
 }
+
+/**
+ * The directive can inject an query that would reflect a list of ancestor directives
+ */
+export class Query extends DependencyAnnotation {
+  directive;
+  @CONST()
+  constructor(directive) {
+    super();
+    this.directive = directive;
+  }
+}