feat(package): introduce a catch-all package angular.

modules/angular has no implementation, but depends on all the pieces
that make angular - core, di, directives, etc. It is the package that
all client apps will depend on.

modules/benchmarks/pubspec.yaml

@@ -2,6 +2,8 @@ name: benchmarks
 environment:
   sdk: '>=1.4.0'
 dependencies:
+  angular:
+    path: ../angular
   facade:
     path: ../facade
   di:

modules/benchmarks/src/tree/tree_benchmark.js

@@ -1,6 +1,6 @@
 import {Parser, Lexer, ChangeDetector} from 'change_detection/change_detection';
 
-import {bootstrap, Component, Template, TemplateConfig, ViewPort, Compiler} from 'core/core';
+import {bootstrap, Component, Template, TemplateConfig, ViewPort, Compiler} from 'angular/angular';
 
 import {CompilerCache} from 'core/compiler/compiler';
 import {DirectiveMetadataReader} from 'core/compiler/directive_metadata_reader';