feat(query): add filter and reduce to QueryList

Closes #4710

modules/angular2/src/core/linker/query_list.dart

@@ -22,11 +22,6 @@ class QueryList<T> extends Object
     return _results.toString();
   }
 
-  List map(fn(T)) {
-    // Note: we need to return a list instead of iterable to match JS.
-    return this._results.map(fn).toList();
-  }
-
   /** @internal */
   void reset(List<T> newList) {
     _results = newList;

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

@@ -37,10 +37,25 @@ export class QueryList<T> {
   get last(): T { return ListWrapper.last(this._results); }
 
   /**
-   * returns a new list with the passsed in function applied to each element.
+   * returns a new array with the passed in function applied to each element.
    */
   map<U>(fn: (item: T) => U): U[] { return this._results.map(fn); }
 
+  /**
+   * returns a filtered array.
+   */
+  filter(fn: (item: T) => boolean): T[] { return this._results.filter(fn); }
+
+  /**
+   * returns a reduced value.
+   */
+  reduce<U>(fn: (acc: U, item: T) => U, init: U): U { return this._results.reduce(fn, init); }
+
+  /**
+   * converts QueryList into an array
+   */
+  toArray(): T[] { return ListWrapper.clone(this._results); }
+
   [getSymbolIterator()](): any { return this._results[getSymbolIterator()](); }
 
   toString(): string { return this._results.toString(); }