feat(compiler): add change detector generation

Runtime and Codegen.

Part of #3605
Closes #4057

modules/angular2/src/transform/template_compiler/change_detector_codegen.ts

@@ -0,0 +1,14 @@
+import {
+  ChangeDetectorDefinition,
+} from 'angular2/src/core/change_detection/change_detection';
+
+// Note: This class is only here so that we can reference it from TypeScript code.
+// The actual implementation lives under modules_dart.
+// TODO(tbosch): Move the corresponding code into angular2/src/compiler once
+// the new compiler is done.
+export class Codegen {
+  generate(typeName: string, changeDetectorTypeName: string, def: ChangeDetectorDefinition): void {
+    throw "Not implemented in JS";
+  }
+  toString(): string { throw "Not implemented in JS"; }
+}