cleanup: move DomAdapter from angular2/core into angular2/platform/common_dom

BREAKING CHANGE

Before

import {DomAdapter} from 'angular2/core';

After

import {DomAdapter} from 'angular2/platform/common_dom';

Closes #5370

modules/angular2/src/testing/matchers.dart

@@ -4,7 +4,7 @@ import 'dart:async';
 
 import 'package:guinness/guinness.dart' as gns;
 
-import 'package:angular2/src/core/dom/dom_adapter.dart' show DOM;
+import 'package:angular2/src/platform/dom/dom_adapter.dart' show DOM;
 
 Expect expect(actual, [matcher]) {
   final expect = new Expect(actual);

modules/angular2/src/testing/matchers.ts

@@ -1,4 +1,4 @@
-import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {DOM} from 'angular2/src/platform/dom/dom_adapter';
 import {global} from 'angular2/src/facade/lang';
 
 

modules/angular2/src/testing/test_component_builder.ts

@@ -18,7 +18,7 @@ import {
 import {el} from './utils';
 
 import {DOCUMENT} from 'angular2/src/platform/dom/dom_tokens';
-import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {DOM} from 'angular2/src/platform/dom/dom_adapter';
 
 import {DebugElement, DebugElement_} from 'angular2/src/core/debug/debug_element';
 

modules/angular2/src/testing/test_injector.ts

@@ -19,7 +19,7 @@ import {DynamicComponentLoader} from 'angular2/src/core/linker/dynamic_component
 import {XHR} from 'angular2/src/compiler/xhr';
 import {NgZone} from 'angular2/src/core/zone/ng_zone';
 
-import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {DOM} from 'angular2/src/platform/dom/dom_adapter';
 
 import {EventManager, EVENT_MANAGER_PLUGINS} from 'angular2/core';
 import {MockDirectiveResolver} from 'angular2/src/mock/directive_resolver_mock';

modules/angular2/src/testing/testing_internal.ts

@@ -1,4 +1,4 @@
-import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {DOM} from 'angular2/src/platform/dom/dom_adapter';
 import {StringMapWrapper} from 'angular2/src/facade/collection';
 import {global, isFunction, Math} from 'angular2/src/facade/lang';
 import {NgZoneZone} from 'angular2/src/core/zone/ng_zone';

modules/angular2/src/testing/utils.ts

@@ -1,5 +1,5 @@
 import {ListWrapper, MapWrapper} from 'angular2/src/facade/collection';
-import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {DOM} from 'angular2/src/platform/dom/dom_adapter';
 import {isPresent, isString, RegExpWrapper, StringWrapper, RegExp} from 'angular2/src/facade/lang';
 
 export class Log {