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

Additional clean up of query code.

Closes: #1935

BREAKING CHANGE:
By default Query only queries direct children.

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); }
 }

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

@@ -35,9 +35,9 @@ import {BaseQueryList} from './base_query_list';
  * with `<tabs>`
  * component's on `hydrate` and deregister on `dehydrate` event. While a reasonable approach, this
  * would only work
- * partialy since `*ng-for` could rearange the list of `<pane>` components which would not be
+ * partialy since `*ng-for` could rearrange the list of `<pane>` components which would not be
  * reported to `<tabs>`
- * component and thus the list of `<pane>` componets would be out of sync with respect to the list
+ * component and thus the list of `<pane>` components would be out of sync with respect to the list
  * of `<pane>` elements.
  *
  * A preferred solution is to inject a `QueryList` which is a live list of directives in the