feat(query): adds support for descendants and more list apis.

Additional clean up of query code.

Closes: angular#1935

BREAKING CHANGE:
By default Query only queries direct children.

Author: rkirov

modules/angular2/src/core/annotations_impl/annotations.ts

@@ -231,14 +231,13 @@ import {DEFAULT} from 'angular2/change_detection';
  *
  * ### Injecting a live collection of descendant directives
  *
- * Note: This is will be implemented in later release. ()
- *
- * Similar to `@Query` above, but also includes the children of the child elements.
+ * By passing the descendant flag to `@Query` above, we can include the children of the child
+ * elements.
  *
  * ```
  * @Directive({ selector: '[my-directive]' })
  * class MyDirective {
- *   constructor(@QueryDescendents(Dependency) dependencies:QueryList<Dependency>) {
+ *   constructor(@Query(Dependency, {descendants: true}) dependencies:QueryList<Dependency>) {
  *   }
  * }
  * ```

modules/angular2/src/core/annotations_impl/di.ts

@@ -1,5 +1,6 @@
-import {CONST, stringify} from 'angular2/src/facade/lang';
+import {CONST, stringify, isPresent} from 'angular2/src/facade/lang';
 import {DependencyAnnotation} from 'angular2/src/di/annotations_impl';
+import {resolveForwardRef} from 'angular2/di';
 
 /**
  * Specifies that a constant attribute value should be injected.
@@ -53,6 +54,13 @@ export class Attribute extends DependencyAnnotation {
  */
 @CONST()
 export class Query extends DependencyAnnotation {
-  constructor(public directive: any) { super(); }
+  descendants: boolean;
+  constructor(private _directive: any, {descendants = false}: {descendants?: boolean} = {}) {
+    super();
+    this.descendants = descendants;
+  }
+
+  get directive() { return resolveForwardRef(this._directive); }
+
   toString() { return `@Query(${stringify(this.directive)})`; }
 }

modules/angular2/src/core/compiler/base_query_list.dart

@@ -46,4 +46,8 @@ class BaseQueryList<T> extends Object with IterableMixin<T> {
   removeCallback(callback) {
     this._callbacks.remove(callback);
   }
+
+  get length => this._results.length;
+  get first => this._results.first;
+  get last => this._results.last;
 }

modules/angular2/src/core/compiler/base_query_list.ts

@@ -1,4 +1,4 @@
-import {List, MapWrapper, ListWrapper} from 'angular2/src/facade/collection';
+import {List, ListWrapper, MapWrapper} from 'angular2/src/facade/collection';
 
 /**
  * Injectable Objects that contains a live list of child directives in the light Dom of a directive.
@@ -10,9 +10,9 @@ import {List, MapWrapper, ListWrapper} from 'angular2/src/facade/collection';
  * @exportedAs angular2/view
  */
 export class BaseQueryList<T> {
-  _results: List<T>;
-  _callbacks;
-  _dirty;
+  protected _results: List<T>;
+  protected _callbacks;
+  protected _dirty;
 
   constructor() {
     this._results = [];
@@ -43,4 +43,10 @@ export class BaseQueryList<T> {
   onChange(callback) { ListWrapper.push(this._callbacks, callback); }
 
   removeCallback(callback) { ListWrapper.remove(this._callbacks, callback); }
+
+  get length() { return this._results.length; }
+
+  get first() { return ListWrapper.first(this._results); }
+
+  get last() { return ListWrapper.last(this._results); }
 }