feat(core): separate refs from vars.

Introduces `ref-` to give a name to an element or a directive (also works for `<template>` elements), and `let-` to introduce an input variable for a `<template>` element.

BREAKING CHANGE:
- `#...` now always means `ref-`.
- `<template #abc>` now defines a reference to the TemplateRef, instead of an input variable used inside of the template.
- `#...` inside of a *ngIf, … directives is deprecated.
  Use `let …` instead.
- `var-...` is deprecated. Replace with `let-...` for `<template>` elements and `ref-` for non `<template>` elements.

Closes #7158

Closes #8264

modules_dart/angular2_testing/test/angular2_testing_test.dart

@@ -36,7 +36,7 @@ class ExternalTemplateComponent {
 class MyToken {}
 
 const TEMPLATE =
-    '<div><copy-me template=\'ngFor #item of items\'>{{item.toString()}};</copy-me></div>';
+    '<div><copy-me template=\'ngFor let item of items\'>{{item.toString()}};</copy-me></div>';
 
 void main() {
   initAngularTests();

modules_dart/transform/lib/src/transform/common/ng_compiler.dart

@@ -2,6 +2,7 @@ library angular2.transform.template_compiler.ng_compiler;
 
 import 'package:angular2/src/compiler/config.dart';
 import 'package:angular2/src/compiler/view_compiler/view_compiler.dart';
+import 'package:angular2/src/core/console.dart';
 import 'package:angular2/src/compiler/html_parser.dart';
 import 'package:angular2/src/compiler/style_compiler.dart';
 import 'package:angular2/src/compiler/offline_compiler.dart';
@@ -31,6 +32,7 @@ OfflineCompiler createTemplateCompiler(AssetReader reader,
       parser,
       new DomElementSchemaRegistry(),
       _htmlParser,
+      new Console(),
       [new RouterLinkTransform(parser)]);
 
   return new OfflineCompiler(