docs(dart): update to b12

Also update dart_to_js_script_rewriter dependency to ^1.0.1,
and change most angular2.dart imports to be core.dart instead.

The pipes example broke without the angular2.dart import, so I let it be.

The server-communication sample has never worked for me,
so I changed it but might have broken it further.

closes #1007

Author: kwalrath

public/docs/_examples/architecture/dart/lib/backend_service.dart

@@ -1,5 +1,5 @@
 // #docregion
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 import 'hero.dart';
 import 'logger_service.dart';

public/docs/_examples/architecture/dart/lib/hero_detail_component.dart

@@ -1,5 +1,5 @@
 // #docregion
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 import 'hero.dart';
 

public/docs/_examples/architecture/dart/lib/hero_list_component.dart

@@ -1,5 +1,5 @@
 // #docplaster
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 import 'hero.dart';
 import 'hero_detail_component.dart';

public/docs/_examples/architecture/dart/lib/hero_service.dart

@@ -1,4 +1,4 @@
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 import 'backend_service.dart';
 import 'hero.dart';

public/docs/_examples/architecture/dart/lib/logger_service.dart

@@ -1,7 +1,7 @@
 // #docregion
 import 'dart:html';
 
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 /// A service for logging messages of various types.
 ///

public/docs/_examples/architecture/dart/pubspec.yaml

@@ -5,9 +5,9 @@ version: 0.0.1
 environment:
   sdk: '>=1.13.0 <2.0.0'
 dependencies:
-  angular2: 2.0.0-beta.11
+  angular2: 2.0.0-beta.12
   browser: ^0.10.0
-  dart_to_js_script_rewriter: ^0.1.0
+  dart_to_js_script_rewriter: ^1.0.1
 transformers:
 - angular2:
     platform_directives: 'package:angular2/common.dart#CORE_DIRECTIVES'

public/docs/_examples/attribute-directives/dart/lib/app_component.dart

@@ -1,5 +1,5 @@
 // #docregion
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 import 'highlight_directive.dart';
 

public/docs/_examples/attribute-directives/dart/lib/highlight_directive.dart

@@ -1,6 +1,6 @@
 // #docplaster
 // #docregion full
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 @Directive(selector: '[my-highlight]', host: const {
   '(mouseenter)': 'onMouseEnter()',

public/docs/_examples/attribute-directives/dart/lib/highlight_directive_1.dart

@@ -1,7 +1,7 @@
 // #docregion
 library attribute_directives.highlight_directive;
 
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 @Directive(selector: '[my-highlight]')
 class Highlight {

public/docs/_examples/attribute-directives/dart/lib/highlight_directive_2.dart

@@ -1,5 +1,5 @@
 // #docregion
-import 'package:angular2/angular2.dart';
+import 'package:angular2/core.dart';
 
 @Directive(selector: '[my-highlight]',
 // #docregion host