feat(dart/transformer:: Initial commit of ctor stubs & annotation register

Closes #646

Closes #496

Closes #498

modules/angular2/test/transform/two_deps_files/foo.dart

@@ -0,0 +1,8 @@
+library foo;
+
+const contextString = 'soup';
+
+class MyContext {
+  final String s;
+  const MyContext(this.s);
+}