feat(transformers): implement initializing deferred libraries

Implement deferred libraries to work with dependency injection and other
angular codegen. This is done by not initializing the library in the parent
ng_deps file when it is declared as deferred, rewriting the import and,
chaining a future that initializes the library in any files that are using
deferred libraries which need angular codegen.

modules/angular2/test/transform/directive_processor/expected/hello.ng_deps.dart

@@ -1,6 +1,7 @@
 library examples.src.hello_world.index_common_dart.ng_deps.dart;
 
 import 'hello.dart';
+export 'hello.dart';
 import 'package:angular2/src/reflection/reflection.dart' as _ngRef;
 import 'package:angular2/angular2.dart'
     show bootstrap, Component, Directive, View, NgElement;