chore(sources): intro modules_dart; move analyzer code there

We have Dart code in `angular2` module that ought to be in its own
package. Examples include Dart analysis plugins, and potentially the
transformers (although transformers cannot be moved out just yet).
However, this code is Dart-only and it doesn’t make sense to use JS
directory layout for it. This commit introduces a sub-directory called
`modules_dart`. All modules in this directory are pure Dart packages
using standard pub directory layout. The code in these packages never
gets transpiled. It is directly copied to `dist` unmodified, except an
adjustment in relative paths in `pubspec.yaml` files.

modules_dart/analysis_plugin/lib/plugin.dart

@@ -0,0 +1,22 @@
+library angular2.src.analysis.analyzer_plugin;
+
+import 'package:analyzer/plugin/plugin.dart';
+
+/// Contribute a plugin to the dart analyzer for analysis of
+/// Angular 2 dart code.
+class AngularAnalyzerPlugin implements Plugin {
+
+  /// the unique indetifier for this plugin
+  static const String UNIQUE_IDENTIFIER = 'angular2.analysis';
+
+  @override
+  String get uniqueIdentifier => UNIQUE_IDENTIFIER;
+
+  @override
+  void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {}
+
+  @override
+  void registerExtensions(RegisterExtension registerExtension) {
+    // TODO(keerti): register extension for analysis
+  }
+}

modules_dart/analysis_plugin/pubspec.yaml

@@ -0,0 +1,11 @@
+name: angular2_analysis_plugin
+version: 0.0.0
+description: Dart analyzer plugin for Angular 2
+environment:
+  sdk: '>=1.9.0-dev.8.0'
+dependencies:
+  angular2: '0.0.0'
+  analyzer: '^0.24.4'
+dependency_overrides:
+  angular2:
+    path: ../../dist/dart/angular2

modules_dart/analysis_server/lib/plugin.dart

@@ -0,0 +1,23 @@
+library angular2.src.analysis.server_plugin;
+
+import 'package:analyzer/plugin/plugin.dart';
+
+/// Contribute a plugin for services such as completions, indexing and refactoring
+/// of Angular 2 dart code.
+class AngularServerPlugin implements Plugin {
+
+  /// the unique indetifier for this plugin
+  static const String UNIQUE_IDENTIFIER = 'angular2.analysis.services';
+
+  @override
+  String get uniqueIdentifier => UNIQUE_IDENTIFIER;
+
+  @override
+  void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {}
+
+  @override
+  void registerExtensions(RegisterExtension registerExtension) {
+    // TODO: register extension for code completions, indexing etc
+
+  }
+}

modules_dart/analysis_server/pubspec.yaml

@@ -0,0 +1,7 @@
+name: angular2_analysis_server
+version: 0.0.0
+description: Dart analyzer server plugin for Angular 2
+environment:
+  sdk: '>=1.9.0-dev.8.0'
+dependencies:
+  analyzer: '^0.24.4'