feat(dart/transform): Add a parser for .ng_deps.dart files and use.

Use the parser in `BindGenerator`
This checkin also removes types from `registerSetters` calls since they
can cause runtime failures (see #886). We will resolve this by
generating change detector classes in the future.

modules/angular2/src/transform/common/asset_reader.dart

@@ -5,6 +5,8 @@ import 'dart:convert';
 
 import 'package:barback/barback.dart';
 
+/// A class that allows fetching code using [AssetId]s without all the
+/// additional baggage of a [Transform].
 abstract class AssetReader {
   Future<String> readAsString(AssetId id, {Encoding encoding});
   Future<bool> hasInput(AssetId id);

modules/angular2/src/transform/common/parser.dart

@@ -13,16 +13,22 @@ import 'registered_type.dart';
 
 export 'registered_type.dart';
 
+/// A parser that reads `.ng_deps.dart` files (represented by [AssetId]s into
+/// easier to manage [NgDeps] files.
 class Parser {
   final AssetReader _reader;
   final _ParseNgDepsVisitor _visitor = new _ParseNgDepsVisitor();
 
   Parser(AssetReader this._reader);
 
+  /// Parses the `.ng_deps.dart` file represented by `id` and all of the `
+  /// .ng_deps.dart` files that it imports.
   Future<List<NgDeps>> parseRecursive(AssetId id) async {
     return _recurse(id);
   }
 
+  /// Parses only the `.ng_deps.dart` file represented by `id`.
+  /// See also [parseRecursive].
   Future<NgDeps> parse(AssetId id) async {
     if (!(await _reader.hasInput(id))) return null;
     var ngDeps = new NgDeps(await _reader.readAsString(id));
@@ -56,6 +62,7 @@ class Parser {
   }
 }
 
+/// The contents of a `.ng_deps.dart` file.
 class NgDeps {
   final String code;
   final List<ImportDirective> imports = [];

modules/angular2/src/transform/common/registered_type.dart

@@ -3,13 +3,17 @@ library angular2.src.transform.common.registered_type;
 import 'package:analyzer/analyzer.dart';
 import 'package:angular2/src/transform/common/names.dart';
 
-/// Represents a call to `Reflector#registerType` generated by
-/// `DirectiveProcessor`.
+/// A call to `Reflector#registerType` generated by `DirectiveProcessor`.
 class RegisteredType {
+  /// The type registered by this call.
   final Identifier typeName;
+  /// The actual call to `Reflector#registerType`.
   final MethodInvocation registerMethod;
+  /// The factory method registered.
   final Expression factory;
+  /// The parameters registered.
   final Expression parameters;
+  /// The annotations registered.
   final Expression annotations;
 
   RegisteredType._(this.typeName, this.registerMethod, this.factory,