feat(dart/transform): Use the best available Change Detectors

Enable pregenerated (for Dart) and JIT (for Js) change detectors when
possible. Previously we would always use `DynamicChangeDetector`s, but
these cause megamorphic calls and are therefore much slower.

Closes #502

modules/angular2/test/transform/integration/two_annotations_files/expected/bar.ng_deps.dart

@@ -20,6 +20,8 @@ void initReflector(reflector) {
         const View(template: 'Salad')
       ]
     });
+  _gen.preGeneratedProtoDetectors['MyComponent_comp_0'] =
+      _MyComponent_ChangeDetector0.newProtoChangeDetector;
 }
 class _MyComponent_ChangeDetector0 extends _gen.AbstractChangeDetector {
   final dynamic _dispatcher;