refactor: rename annotations to metadata

BREAKING CHANGE (maybe)

Well as long as our customers use public API this should not be a
breaking change, but we have changed import structure as well as
internal names, so it could be breaking.

import:
  angular2/annotations => angular2/metadata

Classes:
  *Annotations => *Metadata
  renderer.DirectiveMetadata => renderer.RendererDirectiveMetadata
  renderer.ElementBinder => renderer.RendererElementBinder
  impl.Directive => impl.DirectiveMetadata
  impl.Component => impl.ComponentMetadata
  impl.View => impl.ViewMetadata

Closes #3660

modules/angular2/test/transform/common/ng_meta_test.dart

@@ -8,10 +8,10 @@ main() => allTests();
 
 void allTests() {
   var mockData = [
-    new DirectiveMetadata(id: 'm1'),
-    new DirectiveMetadata(id: 'm2'),
-    new DirectiveMetadata(id: 'm3'),
-    new DirectiveMetadata(id: 'm4')
+    new RenderDirectiveMetadata(id: 'm1'),
+    new RenderDirectiveMetadata(id: 'm2'),
+    new RenderDirectiveMetadata(id: 'm3'),
+    new RenderDirectiveMetadata(id: 'm4')
   ];
 
   it('should allow empty data.', () {